I travel with rabbits over long distances, mostly by automobile.
When driving we stop about every 4 hours and set up an exercise pen for them to use the bathroom, eat and drink for about 30 minutes. Eating hay or grass is most important. Sometimes they don't drink, but always give them enough time to eat.
In my experience, rabbits normally prefer a somewhat snug travel carrier. So two dwarf rabbits in hand luggage (i.e. a soft carrier) on an airplane is probably fine for a couple hours. Potty, water and hay, breaks as you enter and exit the airport would be necessary.
Some rabbits will not eat while in a moving vehicle. This makes it more important that you have stops to eat hay, also have hay in the carrier.
If the rabbit has to travel in the hold of the plane (as looks like is required in your case per the comment by SerenaT) it will be very stressful, and stress kills rabbits so I would NOT recommends this option.
As long as your bunnies are getting hay breaks, and not getting overheated. They can stay in snug travel carriers at all time there is movement.
If your rabbits are bonded (live together in the same space without fighting) they should always travel in the same carrier.
If they are not bonded, it depends... If you are traveling long distances with unbonded rabbits and thinking about keeping them in the same carrier ask a new question just about that.
Trying to find a foldable carrier that works as a playroom and carrier is going to be challenging. For times where you have room to stretch out but are not at home google for 'soft foldable rabbit pen' I have seen several different versions of these in operation, they work well if you are there to supervise. There are several price points, and they fold small for travel. I have seen rabbits spend several hours in them, while people were around.