I just learnt about a new travel cot option today: The PeaPod. I've not seen one of these in person because they aren't available here in Australia, but they look like an excellent idea.
They are a tent-style fold out cot, which is completely zip-up-able, so can keep out the little biting insects. They come with either a pump/blow up air mattress (and its pump), or a self inflating mattress, depending on the model you choose. I'd probably go with the self inflating one - it looks a little more sturdy. A cot-size fitted sheet would probably fit perfectly, and teamed with a cot sheet and blanket (if needed) your kid will be ready for some ZZZZs!
The PeaPod P102 model (which is the one that I think looks the best) weighs only 4.5lb/2kg, which is an excellent, light weight. The models with more features such as a sleeping bag are a bit heavier. They easily pack up into a disc shape, and have their own carry bag for storage and carrying. From the video sequences on the website, it looks like it is VERY quick and easy to both put up and down - definitely one for the dummies or even just the tired parents who have grumpy kids that need a sleep NOW!!
47"L x 30"W x 19"H / 121.92cm x 76.2cm x 45.72cm
Storage bag dimensions:
14"L x 5"W x 14"H / 35.56cm x 12.7cm x 35.56cm
Going by the length of the opened out cot, you could easily fit a child who is up to 2-3 years of age in there (as long as they are not exceptionally tall!) with room for them to move.
The side (door) zips down, so provides easy access for you to get to your crying baby, or for tucking your kid in, or for the older child to get out to go to the toilet by themself.
All the sides have mesh "windows" for good cross flow of air, but if you needed to close it up a bit (so the child can't see out so well and be distracted by the rest of the world) you could easily throw a sheet over it to block the view a bit. The fabric is also apparently good for UV protection - not sure if that is just the main fabric or the window mesh as well.
From the type of construction that it is, I cannot imagine that you would have any trouble getting this onto a plane as part of your carry-on luggage. (Of course I can't guarantee that - because who knows whether the powers-that-be would agree with me!) But to me it seems like there is nothing in its construction (such as chunky metal poles) that could be construed as a weapon, so you should be able to take it in cabin with you, if you are travelling the one-bag way with cabin luggage only. However, I don't recommend you try to use it during the flight itself...!
There are a few different models at different price points, so you can choose what suits your needs and budget.
All in all, this looks like a really good product, which would be perfect for road or plane trips. Just whip it out, put it up indoors or out, and its kiddie sleep time. Sweet dreams!