There’s one thing besides your identification you should never leave home. It’s your electronic ticket number.

Electronic or e-tickets as they are called, are getting to be standard. Most U.S and European carriers won’t issue paper tickets anymore, and if they do, they generally charge extra. And IATA – the International Air Transport Association – is close to their goal of 100 percent e-tickets. Even skeptical travelers have become used to the concept and are relaxing about not having paper in hand.

But don’t get too relaxed. Especially if your itinerary includes more than one airline.

I just got another call from a client at the airport. And it happens at least once a month, sometimes once a week.. She flew out on Northwest to Boston via Minneapolis, and was flying home on United. The gate agent told her “You don’t have a ticket,” and wanted her to buy a new one.

Fortunately, this client called me, and I gave her the ticket number. I could hear in the background “Oh, there it is.” And she got her boarding pass.

Had I or another agent not been available, we would have had to hash it out with United and/or Northwest’s refund department.

Most e-tickets work smoothly. But if you are in the minority when they don’t, it’s no fun. I missed a plane myself earlier this year because a Delta agent couldn’t pull up a United electronic ticket on a close connection in time for the flight.

Besides having more than one airline on the ticket, other factors that increase the chances of a problem include having changed your ticket, having made a reservation that was canceled at any time before you bought your ticket and having had any schedule changes on the ticket.

If the fare allows, ticketing each airline separately helps with check-in, though this may expose you to secondary screening because the airline will show it as one way tickets. But having that ticket number in hand, whether as a receipt or a printout, will definitely increase your chances of solving any problem.

And the trip you save may be your own.

photo by matt.hintsa on flickr