Air Travel on Fast Days – Part Three by Rabbi Chaim Jachter


For the past two weeks, we have been examining the fascinating questions regarding air travel on a fast day.  We mentioned that eastbound travelers who encounter nightfall will have their fast day shortened, and westbound air travelers will find their fasts extended, though there might be a potential for such travelers to conclude their fasting before nightfall.  We also noted that one who crosses the dateline has entered the new day in accordance with his new location.  Thus, westbound travelers who cross the dateline will have their fast day shortened and possibly avoid it altogether.  This week, we shall complete this series with a discussion of the location of the dateline, the possibility of eastbound travelers reentering the fast after crossing the dateline, and an eastbound plane that encounters nightfall and then returns westward and reenters the fast day.  

Location of the Dateline 

Although we concluded that one enters the new day when crossing the dateline, Poskim vigorously debate the location of the dateline according to Halachic standards (see the no less than thirteen opinions outlined in the appendix to volume 22 of the Encyclopedia Talmudit).  The three basic opinions (outlined in an essay that appears at and in the appendix to volume 22 of the Encyclopedia Talmudit) are that it lies 90 degrees east of Yerushalayim (Chazon Ish), 180 degrees from Yerushalayim (Rav Yechiel Michal Tukachinsky) or that we may follow the international dateline located 180 degrees from Greenwich, England (Rav Zvi Pesach Frank).  Rav Hershel Schachter is strongly inclined to follow the opinion of the Chazon Ish (BeIkvei HaTzon page 67), while Rav Elazar Meyer Teitz told me that Rabbanim of the previous generation regarded the Chazon Ish’s view as a minority opinion.  Thus, one must consult his Rav for a ruling regarding this matter.

We should also add that Rav Schachter (ad. loc.) rules that the dateline for air travelers differs from the dateline for those on land.  The Chazon Ish rules that the dateline hugs the eastern coastline for those continents through which the Halachic dateline passes according to his opinion (Asia and Australia).  He reasons that “Ein Mechalkin HaYabashot,” we do not split a continent as partly on one side of the dateline and partly on the other side.  Accordingly, the Chazon Ish regards Sydney and Melbourne (located on the eastern coast of Australia) as being west of the dateline even though they are located further than ninety degrees east of Yerushalayim. 

Rav Schachter reasons that this logic applies to one who is located on land, not to one traveling in the air.  Thus, according to Rav Schachter, one who embarks on a plane trip from Melbourne or Sydney on Sunday enters Shabbat immediately upon takeoff!  One should consult his Rav about this matter, and specifically regarding how air travelers should manage the crossing of the dateline.  Fortunately, it is common today for planes to display on a screen precisely where the plane is located, thereby making it easier for one to determine a Halachically appropriate course of action.  

Traveling East and Crossing the Dateline

Most eastbound air travelers will find their fast curtailed, as we discussed two weeks ago.  However, one who has completed the fast of Shiva Asar BeTammuz in a community that lies west of the dateline, such as Singapore or Hong Kong, and boards an eastbound flight will again encounter the seventeenth day of Tammuz once he has crossed the dateline (as one who crosses the dateline from west to east “gains” a day).

We should note that there is a precedent for observing a holiday twice in one year.  If one is located in Tel Aviv on the fourteenth of Adar and Yerushalayim on the fifteenth of Adar, the Chazon Ish (Orach Chaim chapter 152 where further details are presented) writes that in such a situation one would be obligated to observe Purim on both days.

It seems, though, that those who follow and further apply the ruling of the Nachal Eshkol that we cited last week justifying the practice in Stockholm to conclude Shiva Asar BeTammuz at 9:30 even though nightfall is yet to come would rule that we never accepted an obligation to fast Shiva Assar BeTammuz twice within a 24-hour period. 

Rav Asher Bush (Teshuvot Sho’el BeShlomo number 40) addresses this question in the context of Taanit Ester (which, admittedly, is treated more leniently by Poskim, see Rama to 686:2 and the essay discussing Taanit Esther available at  He cites the Beit Yosef (O.C. 686 s.v. UMah SheKatav), who writes that we do not commemorate Ester’s three day fast with three days of fasting “in order not to impose too much of a burden on the community,” and criticizes as excessive (ad. loc. s.v. Katuv, citing the Shibolei HaLeket) those who fast Taanit Ester on both Thursday and Friday when Purim falls out on Sunday. Rav Bush considers these to be precedents for not requiring an eastbound traveler to resume fast when he reenters the thirteenth of Adar.  He argues that we never accepted the custom to fast Taanit Ester for two days.

It seems that the same can be said for Shiva Asar BeTammuz, Tzom Gedaliah, and Asara BeTeiveit, which we in current circumstances observe due to custom (as we explained last week).  Rav Hershel Scahcter told me that he agrees with this ruling.  Furthermore, Shiva Asar BeTammuz, Tzom Gedaliah and Asara BeTeiveit are described in the Navi Zechariah (8:19) as Tzom HaRevii, Tzom HaShevii, and Tzom HaAsiri (the fast of the fourth month, the fast of the seventh month, and the fast of the tenth month), respectively.  Rav Schachter infers that by definition there is an obligation (stemming from the Pasuk in Zechariah) to fast only once in the fourth month (i.e. Tammuz), seventh month (Tishrei), and tenth month (Teiveit). 

The Gerrer Rebbe (in a responsum that appears in Piskei Teshuvot, number 252, which was published in 5697) discusses one who embarks on Motzaei Yom Kippur and reenters Yom Kippur in the air.  He writes that on a Biblical level, one is not obligated to resume fasting.  He bases his assertion on the Pasuk (Vayikra 23:32) that presents the obligation to fast on Yom Kippur as “MeiErev Ad Erev,” “From evening to evening.”  Thus, it seems that one does not enter Yom Kippur that already is in progress if he was not in that location in the evening at the beginning of the fast.  The Gerrer Rebbe, though, implies that rabbinic law requires one to resume fasting if he has reentered Yom Kippur.  This does not imply that rabbinic law requires one to fast upon reentering Shiva Asar BeTammuz, Tzom Gedaliah, or Asara BeTeiveit, since these fasts are not rooted in Biblical law and are not treated nearly as strictly as Yom Kippur. 

Teshuvot Eretz Zvi (number 44) believes that an air traveler does not join Shabbat in progress, since the Halachic status of many items is determined by its status at the beginning of Shabbat. This applies to a variety of areas, including the laws of Muktzeh and Eruvei Chatzeirot and Techumin (see Eretz HaTzvi chapter seven where Rav Schachter develops this at length).  Rav Schachter (Eretz HaTzvi ad. loc.) believes that nonetheless, rabbinic law obligates one who has entered Shabbat in progress to observe Shabbat. 

These exceptions of not joining Shabbat or Yom Kippur in progress do not seem to apply to all other areas of Halacha, as both have unique considerations that preclude entering them in progress.  Thus, it would seem that if one who was traveling westward on the sixteenth of Tammuz or ninth of Tevet crosses the dateline, he must join the fast in progress.  Indeed, Rav Schachter believes that such an individual enters the new day, thereby requiring him to don Tefillin and daven Mincha, as we noted last week.  Thus, it would seem that he should also begin to fast once he has entered the dateline.

An Eastbound Plane that Returns Westward

I was told of a situation where a plane that headed east on a fast day encountered nightfall (whereupon the observant Jewish passengers ended their fast) and then, due to engine trouble, needed to return to New York. The passengers were consequently returned to daylight and the date of the fast.  The question was whether they were obligated to return to the fast that they had begun.  Perhaps one could say also say, similar to the Nachal Eshkol, that we never accepted an obligation to fast in such a situation.  Rav Schachter told me that he agrees that once the fast has terminated, one is not obligated to begin it again (even if one does not accept the Nachal Eshkol’s justification of the practice in Stockholm).


From our discussions of the past weeks, several points emerge.  Eastbound air travelers who do not cross the dateline may end their fast when they encounter nightfall according to nearly all Poskim.  There is, however, considerable dispute regarding when westbound air travelers (who do not cross the date line) must conclude their fast later.  Fasts appear to conclude (or begin) when crossing the dateline from east to west, but there is considerable dispute regarding the location of the dateline as defined by Halacha.  One who has already observed these three fasts does not return to the fast when crossing the dateline from west to east.  One should consult his Rav for a ruling regarding the points of dispute.  We should conclude by noting that except for the question regarding eastbound travelers who do not cross the dateline, Poskim are considerably stricter regarding Yom Kippur and Tisha BeAv.

Explaining an Obscure Aggadic Passage by Rabbi Chaim Jachter

Air Travel on Fast Days – Part Two by Rabbi Chaim Jachter