Since you are a beginner and just starting to learn various arrangements of the songs you want to play, you should be able to use a 61 key keyboard and derive plenty of enjoyment. You won't be able to play the composers arrangements of classical standards, but that does not sound like your goal.
61 keys gives you enough keys to play a bass line or some chords with your left hand and play the melody and/or counterpoint with your right. Some keyboards allow for transposing or shifting of the tuning in a split keyboard arrangement to give you a wider range on 61 keys.
The fact that you want to carry your instrument on a plane is a big reason that I feel the 61 key version should be strongly considered. That is probably the only size that you might have a chance at carrying on and stowing in the overhead compartment of an airplane. I fly with a guitar and carry it on. And my 61 key Casio keyboard is shorter than my guitar. So I'm thinking maybe ...
If you can get a keyboard that will fit in a padded keyboard soft bag that can qualify as carry on luggage, then I would go that route and carry it on so you can keep an eye on it. If you end up with a keyboard that is too big to carry on, invest in a sturdy, hardshell, flight case and consider insurance if it's available. The baggage handlers can be pretty rough, tossing your keyboard around.
Play different keyboards to see how they feel to you. They all vary from make to make and within brands, there may be different offerings with a different feel on the keys. I would tend to lien towards one of the lower priced instruments that met my needs if I were going to use it as a traveler and carry it on a plane.
Most accomplished professional musicians who get paid to tour all over the country or world, have their promoters arrange to have a rental keyboard or piano delivered to each venue. It's really hard to travel with a nine foot Steinway Grand Piano - or even a Hammond B-3 Organ. So when you reach that level, you will be playing a full sized instrument, but will be renting it at your destination.
Have fun learning to play some songs you enjoy on a smaller keyboard. It should work just fine for now.