If flying during Pessach and a meal is offered, often it won't be Kosher for Pessach.
If possible, try ordering a fruit platter.
If the ticket has not been ordered yet, have Kavono not to be Koyne the ticket.*
Not accepting the meal does not help, as allocated already.
The fact that a special meal is in fact, only a request and not an obligation to the airline, does not help.
*I know it sounds weird, but I told