Safe to fly with 6 week old kittens? Grateful for professional advice!

Dear vets and cat lovers, I would very much appreciate your advice on flying with kittens and more specifically: 'from what age is it safe to fly with kittens when they travel together with their mum (lungs, ears etc. developed enough to handle cabin pressure)'? + 'what is the earliest age kittens can safely receive the rabies vaccination'? + 'what is the earliest age kittens can get chipped'? We need to go back home after some months on an island and would like to take our sweet little cat family with us (2h flight from Madeira to Portugal mainland). Naya, the mummy cat was a stray and found us when she was pregnant. Now she has 3 kittens that are 3 weeks old. We love them so much! Also, she's so attached and in trust by now, that we don't want to leave her behind here in any way. We have chipped and vaccined the mummy cat. Now we are not sure when it is safe to travel with them? The local vet told us that the babies don't need chip + vaccine if travelling with their mum and also that it would be ok for the kittens to fly at 4 weeks age (which seemed a bit too easy and too young to us). The airline now says they all 4 need to be chipped and vaccined (even though its a domestic flight). We know that the rabies vaccine is normally given at 12 weeks age but have no option to stay on the island for another 9 weeks until they are old enough for that. What can we do? Thank you so much in advance for sharing your insights. We need to go home asap (latest in 3 weeks when the kittens are 6 weeks old) and appreciate your support in finding a good solution without putting the kittens at risk. Many many thanks!!!

Hello!   We are a UK site and so not experts in the rules about flying between Madera and Portugal.  The import and expert laws of the respective countries must obviously be followed and the airline will have the final say as to whether they will be prepared to carry this precious cargo or not. You could ask them to clarify where they take their advice from in this decision and, for sure, what specific diseases they would like the cats to be vaccinated against.  Having done this, you could ask your local vet (the exact details will depend on the vaccine company) at what age the relevant vaccinations can be safely given and when the vaccination will be fully effective.  I don't know of an effective 'flu vaccine, let a lone a Rabies vaccine, where even the first vaccine is given at such a young age.  Therefore, I suspect that the kittens may have to stay in Madeira for significantly longer.