Airline credit and change fee

I recently bought a departure and return ticket from NY To Tampa and I had to cancel my flights. I got a credit of 239 for one ticket and the other I got a credit of 291. Now both tickets are with different airlines so the change fee is 150 for one and 200 for the other. How do I make the most of my credit now for when I want to book another flight (any destination). I just want to make this as cost efficient as possible.

Any credit you have with either airline, can only be used on booking with the individual airline, you won't be able to combine it. You need to check the terms, as sometimes credits are time limited, i.e. They could be valid for up to a year, after that any unused credit is void.

Not exactly sure how you want to make this as cost efficient, as they are with two different airlines so you can only use the credit with each airline.

If you are worried about not using the entire credit, then the only way to guarantee that you do is to find a flight that is more than your credit with that particular airline. As while you didn't mention the airline, with most airlines the credit can only be used on a single flight so if had a $239 credit but found a flight for $200 you would lose that $39.

Also, be aware that the time you have to use this credit is probably limited to 1 year. But this may not be 1 year from the original flight date. It could be 1 year from the date you cancelled, or even 1 year from the date of original booking. You also generally need to have your travel completed, not just booked by the expiration date. If in doubt contact the airlines directly to find out exactly when they expire.