Who knew that boarding an aircraft would become the newest customer-service issue to rile passengers since the removal of hot meals on flights?

In the past week, two major airlines have altered boarding policies as part of an effort to appease customers while still getting their flights out quicker.

Recently, Southwest Airlines budged on its 35-year policy of no assigned seats. Southwest now is assigning seats to passengers on flights out of San Diego as part of an eight-week trial. The move comes as the carrier is trying to attract more frequent business travelers who avoided the airline because it required passengers to check in for flights at least 24 hours in advance or arrive at the airport hours before departure to be part of the first boarding group with the best shot at preferred seats.

Northwest Airlines two weeks ago week abandoned row-by-row boarding in its coach cabin and opted for open boarding on domestic and Asia-bound flights. That means, after first-class passengers, top members of its frequent-flier program and those needing extra assistance, the rest of the cabin can scramble. Airline spokesman Dean Breest said the change shaves about seven minutes off boarding times.

Boarding has become the latest quandary for airline executives. How do they get passengers on their flights quickly and easily so that the aircraft can close its doors and depart on time? The quicker they can get an aircraft back in the air, the more money that aircraft makes.

Several Northwest customers who flew recently said the boarding change created chaos. Sandra C. Greer flew Northwest to Albuquerque on June 3 but vowed never to fly the airline again because of what she said was a "mad rush" among passengers who jammed the gate area to board.

"It was chaos. I can't imagine how this saves time," said Greer, a chemical and biomolecular engineering professor at the University of Maryland.

But Kate Bauer, a Detroit-based Ford Motor Co. collections analyst, said Northwest's new process was "OK" because passengers rarely paid attention to row boarding announcements and boarded when they wanted anyway.

Random boarding seems to be emerging as the preferred method among airlines in part because it frees gate agents to perform other duties such as helping passengers with seating or flight problems.

JetBlue Airways has used random boarding since this spring. Canada's WestJet has used open boarding since 2002 after trying to find alternatives such as boarding passengers from the front of the coach section to the back and from the back to the front. WestJet even tried nontraditional, whimsical ways, such as boarding passengers based on the color of passengers' hair, shoes or socks. "We have found the most efficient is doing a general boarding call," said WestJet's spokeswoman Gillian Bentley.

Last fall, United Airlines chose "Wilma": window, middle-seat then aisle boarding. Before the switch, United used the most common boarding method, boarding coach passengers from the rear of the aircraft to the front. United spokeswoman Robin Urbanski said the new boarding system shaves about five minutes from its boarding time.

America West boards coach passengers from the back to the front of the aircraft and from the windows to the aisles. The process was developed by the Math Department at Arizona State University in 2003.

Since merging with America West last fall, US Airways will abandon its zone-boarding policy and adopt America West's system.