Volaris ticket purchase
 

Yesterday I tried to purchase tickets on Volaris' web site for a January vacation in Mexico. Everything was fine until I tried to enter the phone number. The site would not accept my phone number. I called the airline and the agent could not explain the problem. He offered to book me, but I declined because at that point it was not possible to compare his pricing what was available on line. Tried to book again, and was denied access to the flights I wanted. I waited a day and tried again. This time the flights were available, and then came across the same problem with the phone number. I then tried to enter the number as an international number with starting with 001 and with no spaces or dashes--eureka! it worked.

A word to the wise: this problem may occur for any purchase on the web site of a non U.S. based airline.