"You should avoid travelling with a child with impetigo until they are better, or 48 hours after they have started on treatment. If it is absolutely essential to travel, ensure to take necessary precautions to avoid spreading the infection." Dr Massoud says.
If you are concerned, contact your airline before you travel to check that you will be allowed to board the plane and you can also request a letter from your GP stating that the child in question is no longer contagious to carry with you while you travel as an extra precaution.