When Seattle-Tacoma International Airport opened its new cellphone waiting lot last Christmas, it was done as an experiment to see whether drivers picking up airport passengers would use it.

Today it's so successful the airport is considering expanding or moving the lot.

The cellphone lot is designed for people coming to Sea-Tac to pick up arriving passengers. Instead of driving around the airport until your passengers are ready to be picked up, you can park for up to 30 minutes in this special lot and wait there until your passengers call your cellphone to say they are ready.

"We're kind of a victim of our own success," said Michael Civitelli, operations manager at the airport. "The lot is always full. It's used around the clock. We've come to the conclusion that it's too small and we need to do things to make it permanent."

The problem, he said, is finding space at the airport.

The lot, which holds 20 cars, is at South 170th Street in front of Doug Fox Parking.

While the airport asks that drivers stay there no longer than 30 minutes, that's not being enforced.

If flights are delayed, Civitelli said, the airport doesn't want to boot waiting drivers out because then they'll circle the airport, causing more congestion.

Sea-Tac joins several other airports that have cellphone lots, including those in Phoenix and Philadelphia. Airport officials don't know how the lot has affected airport congestion. But they say a driver picking up someone at the airport circles the airport drive two to four times, so if 20 cars are idled in the waiting lot, that potentially eliminates 80 drives around the airport.

An airport study earlier this month found that peak times for the cellphone lot are between 4:30 and 6:30 p.m. and around noon.

Susan Gilmore: 206-464-2054