With your explanation it appears that what your ENT doctor told 'Laryngomalaica' is correct. As he said no medical treatment will help. As noisy breathing is time to time it is mild type. So nothing to worry. By the age of 2 years your child is likely to be alright.
With your writing it is not clear whether your baby struggled to breath when the air craft was on run way or after it took off. If it is on the run way then it is not due to Laryngomalacia
problem. There must be some other incidental reason for that. If it is after take off, as the air craft climbs up air concentration itself becomes less and so is the case with oxygen
in it. That could cause breathing problem in such patients. It is better to wait for flying by air till he is 2 years old as his health is important.
Nowadays his noisy breathing is 15 to 20 times a day makes me to suspect whether his nasal passage is slightly narrowed due to allergy
or mild infection leading to reduced amount of air going in.
You can instill 4 drops of saline drops 4 to 6 times a day for 5 to 7 days. If the problem is solved it is fine.
If not show him to the same ENT specialist
who can find out the exact cause for increase in noisy breathing of your child and treat accordingly.