I find there's a lot of things on the menu that aren't Keto suitable.

Bread rolls, potatoes and other starchy veg, and practically any desserts.
I've had some flights where options were pretty much pasta, cous cous, sandwiches, cakes, pizza etc. All Keto unfriendly.

Meat and fish are generally a good thing especially if not covered in sauces. Might be some veg in there that isn't starchy.
Cheese works well, although could be something like pre-packaged Dairylea etc. depending on what's loaded. Better than nothing.
The butter portion could be used on some meat if required!

A few grapes aren't going to affect things too much if they come with the cheese.

Breakfast, if options include sausage, bacon, eggs etc. would work well.

I generally try and bring some snacks with me such as a bar of Green & Blacks 85% chocolate and/or certain nuts.

Perhaps eat in a lounge say in LAX OR JFK (not sure where you're flying from. Some people, who have cooking facilties may even prepare their own meal and bring a Tupperware container on board). Easy to pick low carb products if they've got buffets.