Originally Posted by
Some person
JAL asks for your phone number but gives you no option to specify the country code so they might think that you use a +81 phone number even if you don't.
Yes, I agree with you.
However, if you want to enter a meaningful phone number,
you can enter a phone number with the international access code (prefix 010) from Japan
For example,
You can enter JAL's US contact numer (+1-310-607-4160) as
01013-10607-4160