While free airline meals are becoming rarer these days across the word, international flights will often still serve them. If you have dietary restrictions, you can use the following table to review all your options for major airlines.
Image from puck777
The table covers offerings related to vegan, vegetarian, medical, religious and allergy restrictions. If two airlines have tickets at the same price, you could use their meal offerings to make your choice. Of all the airlines included, Singapore and JAL have the most options.
Once you pick your airline, then you can see if they offer food that fits your diet and make reservations accordingly. You should call the airline a few days before your flight to confirm that your meal request has been taken care of. You can also pack some snacks in case the meal is not enough or doesn't appeal to you. Check out the table in the full post linked below.
The Picky Eaters Guide to Airline Food [Map Happy]