Three key transponder codes are:7500 for hijack, 7600 for radio, 7700 for emergency.

The following mnemonic can be helpful in remembering the codes.  All three codes end in zeros.

• 75 you need a 45, that is you need a gun as you are being hijacked.
• 76 you need a fix, that is your radio is broken.
• 77 you are going to heaven, hopefully not.

Reference(s):

AIM 2018 4-1-20
AIM 2018 6-2-2

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