If one is traveling overnight [i.e. plane, car] what is he to do about lighting Chanukah candles?
A. Background Halachos:
Relying on one’s family’s lighting: One who is staying as a guest in another person’s home during Chanukah, is not obligated to light candles if his wife [or other family member] is lighting on his behalf at home, [and he does not have his own room]. However, one who is away from home and is staying alone, and not by a family or host, is obligated to light candles, even if his wife [or other family member] is lighting for him at home. [Accordingly, one who is traveling and not staying by a host who is lighting candles for that night of Chanukah, is not exempt with the lighting of his family at home.]
If one is not living in a home [i.e. homeless; camping; traveling; in combat], is he obligated to light Chanukah candles? Some Poskim rule that the Mitzvah of lighting Chanukah candles is independent of home ownership or living in a physical house. Such a person must light Chanukah candles in his current location with a blessing, although he is to place the Menorah in an area that the candles will not blow out due to wind prior to being lit a half hour. Other Poskim however rule that the obligation is dependent on living in a home, and one is hence not obligated to light Chanukah candles if he is currently not living in a home. Even according to the stringent opinion, if one is unable to light the candles in an area where it is protected from being extinguished by the wind, then he is to light the candles without a blessing.
Lighting before sunset in times of need: If one will be occupied [after sunset and will hence be unable to light the Menorah at that time], there are opinions who rule that one may light the candles [with a blessing] before sunset, starting from Plag Hamincha. [Plag Hamincha is 11/4 Zmaniyos hours prior to sunset. Practically, one may rely on this opinion in a time of need, and so is done in Shuls which light the Menorah after Mincha, before sunset, and so is done on in all homes on Erev Shabbos. Likewise, Bedieved, if one lit the candles after Plag Hamincha even not in a time of need, he fulfils his obligation. If, however, one lit the candles prior to Plag Hamincha, he does not fulfill his obligation, and is required to extinguish the candles and relight them at the proper time.] When lighting after Plag Hamincha, one must place [before lighting] enough oil for the candle to last for a half hour past nightfall. [If one did not place enough oil to last this amount of time, he is to extinguish the candle and relight it without a blessing after filling it with the proper amount of oil.]
B. The law:
One who will be in transit throughout the night cannot fulfill his obligation with the lighting at home even if he will be traveling alone and his wife will be lighting the Chanukah candles in his home.
Leaving home after Pelag: Thus, if he will be traveling from his home past Pelag Hamincha, then he is to personally light candles at home with a blessing after Pelag Hamincha, making sure to leave enough oil to last 30 minutes after nightfall.
Leaving home before Pelag: If, however, he needs to leave his home before Plag Hamincha, and will not arrive to his destination until after daybreak, then whether or not he is obligated at all in candle lighting is dependent on the debate recorded above regarding one who does not have a home, and practically, he is to try to be stringent and to light candles at his current location within his travels [i.e. at the airport, by a rest stop, etc]. He may choose to light with a blessing, despite there being a debate in this matter. The candles must be lit in a way that the flame will not go out prior to the required time of 30 minutes. In areas that candle lighting is prohibited, such as a plane, train or bus, and one is unable to make a stop in order to light the candles, then one is to light an electric Menorah, or filament flashlight [not LCD/Led], without a blessing.
Arriving to destination home before Alos Hashachar: If one will arrive to his destination home prior to daybreak, then it is best for him to delay lighting until he reaches his destination. A blessing may be said so long as there is someone still awake in the home. This, however, only applies if he will be traveling from home prior to Pelag Hamincha, otherwise it is better for him to light after Pelag Hamincha, then to light at his destination, unless he is certain that he will arrive with plenty of time remaining prior to daybreak.
 See Orchos Chaim [Rishon] Chanukah 18 regarding ship; Maharsham 4:156 regarding a train; Aruch Hashulchan 677:5 regarding a train; Shearim Hametzuyanim 129:8; Tzitz Eliezer 15:29; Az Nidbaru 7:63; Betzel Hachochma 4:127; iskeiy Teshuvos 677:3; Chazon Ovadia Chanukah pp. 156-158; Ratz Katzevi 9
 Michaber 677:1; Rebbe Zeira Shabbos 23a; M”A 677:3; M”B 677:7
Other opinions: Some Poskim rule that in today’s times, being that everyone [Ashkenazim] lights their own candle, Chashad applies in all cases, even if he does not have a room at all, and even if his wife is lighting for him, and hence one may no longer every rely on one’s family, nor on joining the lighting of the Baal Habayis. [Opinion in M”A 677:3; Mahriy Viyaal 31; Maharil 145; Elya Raba 677:1; Derech Hachaim 1; See Kaf Hachaim 677:11; M”B 677:7; Biur Halacha 677 “Letazmo”]
 See Chapter 3 Halacha 3A in Q&A
 M”A 677:3 in name of Mahriy Viyaal 31; Maharil 145; M”B 677:7
 Based on Michaber ibid who states “A guest of which his family is not lighting on his behalf” and the Poskim explain that this refers to one’s wife, and that if she is lighting on his behalf, he is Yotzei. [Mamar Mordechai 677:1; M”B 677:2; Kaf Hachaim 677:1]
 Michaber 677:1 regarding one who has a room with an opening to the outside; M”A 677:3 in name of Mahriy Viyaal 31; Maharil 145; M”B 677:7; Regarding that this applies even if he is married and his wife is lighting for him at home: Tur and Rambam, brought in Kaf Hachaim 677:9
Maharsham 4:146 [even if the Baal Habayis lights]; Chovas Hador 2 footnote 39; Piskeiy Teshuvos 677:1
 Maharsham 4:156; Aruch Hashulchan 677:5; Piskeiy Teshuvos 677:3
The reason: As the payment for the plane/train/bus ticket is considered like one is renting the space, and it is thus similar to a 2nd home, which requires lighting even if one’s wife is lighting for him in his 1st home. [Maharsham ibid] Alternatively, the reason one should light candles is because he is obligated to see candles in order to say the blessing of Sheasa Nissim, he is thus to light his own candles, even when he is technically Yotzei with the lighting at home. [Aruch Hashulchan ibid]
 Orchos Chaim [Rishon] Chanukah 18 regarding ship; Maharsham 4:156; Aruch Hashulchan 677:5; Shaar Shlomo 51; Beis Shearim 362; Shearim Hametzuyanim 129:8; Tzitz Eliezer 9 p. 97; 15:29; Az Nidbaru 7:63, 67; 11:34-2 based on Rishonim and Achronim; Piskeiy Teshuvos 677:3; Mishneh Halachos 7:86; See Nitei Gavriel 2:1; Mikraei Kodesh Chanukah 18; Chazon Ovadia Chanukah p. 156-158
 Possible way of learning Rashi Shabbos 23b that one is exempt from lighting on a ship due to it not being a house [so learns Igros Moshe ibid, unlike Maharsham ibid]; Implication of Tosafus Sukkah 46a “There are people who do not have homes and cannot fulfill the Mitzvah”; Implication of Rambam Chanukah 4:1 “Every home is to light one candle”; Pnei Yehoshua Shabbos 21; Igros Moshe Y.D. 3:14-5; See Rav SZ”A in Minchas Shlomo 2:51; Halichos Shlomo 2:13; Hilchos Chag Bechag Chanukah p. 27
 Rashi ibid even according to Maharsham
 Michaber 672:1
 M”B 671:2; Kaf Hachaim 672:8
 Mahariy Abuhav
 Peri Chadash 672:1; Birkeiy Yosef 672; M”B 672:3 in name of Peri Chadash ibid; Piskeiy Teshuvos 672:2
Other opinions: Some Poskim rule one is not to recite a blessing when lighting prior to sunset. [Miseches Sofrim 20:2; M”A 672:1; Siddur Beis Oved 1; Tefila Ledavid; Chida in Kisei Rachamim chapter 20; Kaf Hachaim 672:10]
 M”B 672:3
This means that one calculates the amount of day hours in the day and then divides that by 12. One then times that by 1.25 hours, which is the number of hours in Plag Hamincha [1 hour and 15 minutes]. Thus, if there are 14-day hours in the day, then each hour when divided into 12 contains 70 minutes, and thus Plag Hamincha would be 1.25 hours times 70 minutes which equals 87.5 minutes prior to sunset.
 Admur in Siddur Hilchos Kerias Shema and 443:4 [that the day is calculated from sunrise to sunset]; Ketzos Hashulchan 27:4; 74:11 and footnote 25; 76:1; So also rules Gr”a; Chok Yaakov and other Poskim
Background: Admur in the Siddur in Hilchos Kerias Shema and 443:4 rules the day is calculated from sunrise to sunset, and so is the custom today of all Jewry. In accordance to this calculation, Plag Hamincha is 1 and ¼ hours prior to sunset, and so rules Ketzos Hashulchan ibid. See also Admur in 261:5; 443:4.
Ruling of Admur in Shulchan Aruch: In 263:6 Admur rules that Plag Hamincha is 1 hour and 15 minutes before nightfall. This is based on 58:3; 89:1 in which Admur rules the day is from Alos until Tzeis. Likewise, in 261:5 where Admur rules that although one may be stringent to accept Shabbos from 1 and ¼ hours prior to sunset, he may not be lenient to light candles until 1 and ¼ hours prior to nightfall. However, in Admur 443:4 he rules it is counted from sunrise until sunset and so rules Admur in the Siddur.
Other opinions: Some Poskim rule Plag Hamincha is 1.25 Zmaniyos hours prior to nightfall. [Chayeh Adam 154:18; M”B 672:3; 679:2; 692:13; Kaf Hachaim 672:9; 692:29]
 Bach; Kaf Hachaim 672:7
 P”M 672 A”A 1; Shaar Hatziyon 672:4; Kaf Hachaim 672:11
 Pashut; Kaf Hachaim 672:1; See M”B 672:4
 Michaber ibid
The reason: As the candles must remain lit during the night time, which is when the publication of the miracle is achievable. [M”B 672:4]
 P”M 672 A”A 1; M”B 672:4; Kaf Hachaim 672:12
The reason: One does not say a blessing, as perhaps it suffices if the candle remains lit for a half hour during Plag Hamincha, as the entire allowance to light the candles during Plag is because we consider it as night. [P”M ibid]
Other Poskim: Some Poskim rule one is to relight the candles with a blessing. [Chayeh Adam 154:18, brought in Kaf Hachaim ibid]
 See above in background
 See above in background
 See Betzel Hachochma 4:127; Piskeiy Teshuvos 677:3
The reason: As the more accepted approach is that every individual is obligated, even if he does not own a home, and furthermore, whenever we light in public we are accustomed today to say a blessing for Pirsumei Nissa. Nonetheless, those who desire to be stringent regarding Safek Brachos may choose to light without a blessing, or to say it with a child under Bar or Bas Mitzvah to educate them in the blessing.
 See Piskeiy Teshuvos 673:1 footnote 6
Lighting a candle and taking a chance that it will be extinguished: Some Poskim [Betzel Hachochma 4:127; Piskeiy Teshuvos 677:3] suggest lighting a single candle with a blessing even in areas that lighting a match is forbidden, and security will extinguish it, and if one will be forced to extinguish it himself, then he is to light it without a blessing. Practically, however, it does not seem reasonable to ask someone to perform an illegal act, offend others and take a chance of getting arrested, and rather in such a situation, Shev Veal Taaseh Adif, and he should rather light a filament flashlight without a blessing.
 Michaber 672:2; Tur 672; Ravayah 972; Hagahos Maimanis brought in M”A 672:6; M”B 672:11
 M”A 672:6; Hagahos Maimanis
 See Shevet Halevi 4:66; Piskeiy Teshuvos 672:2