If I'm taking a long flight on an airplane on a day when permitted activities change at a certain point, e.g. with the start or end of a fast day, or with the start of the chametz prohibition kicking in before Passover, how can I determine the right time to observe the change in status?

Similarly, how can I determine the right time windows in which to pray the morning prayer, afternoon prayer, etc.?

  • 4
    debbie, Welcome to Mi Yodeya! I'm going to take the liberty of drastically generalizing your question, since we've had this sort of very particular question before, and it would be good to have a canonical reference for a real answer. See also judaism.stackexchange.com/questions/12965/… .
    – Isaac Moses
    Feb 24, 2015 at 14:33

2 Answers 2


The Chai Air Tables are a fantastic tool I've used many times and have seen others use many times.

One simply inputs one's flight route (i.e. source, destination, departure date and time) and the website provides a table (including additional columns for each 15-minute interval of delay) of different Halakhically-relevant times.

Here is an example of what their tables provide:

Chai Tables Example

  • I realize this answer may be insufficient as it's simply a link. If necessary, I can remove it.
    – Lee
    Jul 30, 2015 at 4:37
  • 2
    (Re your comment.) No, the question was "How can I find out when to..." and this is an answer ("by using the Chai tables"), not a link to an answer.
    – msh210
    Jul 30, 2015 at 6:15

Check myzmanim.com, which will give you in-flight zmanim charts. Every airline and every flight is different. Essentially, you need to calculate the flight path of the airplane (which can change right before take-off). Then you need to find the zmanim of your current location (that is, the sea-level equivalent of your location.) Those are the zmanim that apply to you in flight.

  • Does it take into account elevation? Mar 1, 2015 at 21:30

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