I will be flying out of Tijuana to Cabo with my two daughters that are under the age of 9. On the US Customs website it states that children under the age of 16 can cross back to the US with a birth certificate. My question is, will the Mexico airlines/security ask for any other form of ID? I'm not sure if this question should go in the Tijuana forum but I am flying to Cabo. Any help would be great!