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.?


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

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  • I realize this answer may be insufficient as it's simply a link. If necessary, I can remove it. – Lee Jul 30 '15 at 4:37
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    (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 '15 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.

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  • Does it take into account elevation? – Shmuel Mar 1 '15 at 21:30

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