In a move that could save air travelers time, more U.S. airports are installing common-use kiosks that allow self-check-in for multiple airlines.

Nine U.S. airports now have the devices to supplement or replace the airlines' own self-check-in kiosks. That's up from two airports five years ago. Among the places they can be found: Seattle-Tacoma, San Francisco, Las Vegas, Washington's Dulles and Maui's Kahului Airport.

Airports own the common-use kiosks and often place them in terminal areas not occupied by an airline. This spreads out travelers away from airline counters, improving the flow of people, says Byford Treanor, an executive at Dallas/Fort Worth. That airport has 51 common-use kiosks. It plans to buy more.

They can be a benefit to a traveler who wants to avoid congestion around an airline counter, or who may have been dropped off far from their airline's ticketing operations.

The move by airports comes as more air travelers, particularly those without checked baggage, are seeking out self-serve electronic check-in.

Self-service kiosks have been around since the late 1990s and dramatically increased after 9/11 as airlines turned to automation to pare their work forces. Nearly 70 percent of business travelers use airport kiosks, says Forrester Research.

Common-use kiosks are widely used in Europe, Asia and Canada. They have been slow to take off in the U.S. because airlines are reluctant to give up the branding benefits of their machines, says aviation consultant Manik Arora.

Airlines also question whether making software updates to the kiosks will be more cumbersome or costly if they rely on the airport to do them.

David Castelveter, of the airlines' trade group Air Transport Association, says "carriers certainly prefer customers using their own machines."

Las Vegas first set up common-use kiosks in late 2003. Now, all of its 180 kiosks are common-use machines shared by 15 air carriers. None of the air carriers at Las Vegas has its own.

"When we first started, the (airlines') reaction was not very good. Over time, some have become more supportive," says Randall Walker, the airport director.

Other airports that have common-use kiosks: New York's John F. Kennedy; Pittsburgh; and Westchester County (New York).

Minneapolis-St. Paul has turned them off while making software changes but will restart them at Humphrey Terminal soon, says David Ruch of that airport.

Kevin Peterson of SITA, an aviation technology firm and a kiosk developer, says several airports that are planning expansions will include them. "We're in a period of rapid adoption," says Peterson.