Your daughter will probably be too heavy and long for the sky cot at this point. Typically, they are for 27 inches and 20 lbs only. So, you can ask, but you will probably have to have her be a total lap baby. I would ask, when you are booking your flights, which flights seem to be the least occupied. In good situations, you can get a whole row for your family or at least an extra seat between you and your hubby. Then, you can lay her down and not have to hold her the whole time. Bulk head seating is also a good idea because you can put her on the floor to play in front of you with toys while you sit in your seats.
My best advice would be to travel when she is sleeping as much as you can. If she is the kind of kid that is stimulated by people, then you may want to travel while she is awake more... A lay over for an overnight never hurts. It gives her a break from your arms and the plane.
Also, pack lots to do, lots to eat and a favorite sleepy object. I started sleeping my daughter with a certain bear every night. and I only let her see it when she is supposed to go to sleep. It call it her "sleepy bear"... I know, really original. LOL. Anyways, she now associates it with sleep. I hand it to her and put her in a sleeping position. This helps her to get the clue and settle down.
I hope this information helps. Oh, and don't forget that the steward(ess)es can be your biggest help. Win them over quickly and they wil help make your journey more successful and easy.
Don't forget about air pressure... have along something she can suck.. a bottle, a sippy, a paccie... something.