WASHINGTON — Passengers stranded for hours aboard planes on the tarmac would still have to depend on the good will of airlines and airports for relief under guidelines adopted by a federal task force Wednesday.

The task force, which was dominated by the airline industry, approved guidelines for model contingency plans for airlines and airports to follow in cases of extended tarmac delays. But the task force's report to Transportation Secretary Mary Peters doesn't recommend a specific limit on how long passengers can be kept waiting without the opportunity to return to a gate.

Nor does the task force recommend that Peters make the guidelines mandatory. Passengers who had hoped for stronger protections were left empty-handed.

"You have to admit that the game is still heavily weighted to business as usual," Kate Hanni, a passenger-rights advocate, told her fellow task force members before voting against adoption of the report.

Rep. Mike Thompson, D-Calif., who has been pushing for a passengers' bill of rights, said voluntary guidelines "are nice window dressing, they don't provide any real guarantees that passengers will not be abandoned on the tarmac."

"The airlines have had over a year to address this issue themselves, and since they have failed to do so, we will continue to work for real requirements that ensure that people have basic rights when they board a plane," he said.

Industry members of the task forces said they needed the flexibility to design their own response plans and not be pinned to a time limit for holding passengers inside planes on the tarmac.

David Castelveter, a spokesman for the Air Transport Association, which represents major airlines, said setting any specific time limit — passenger-rights advocates have pushed for a maximum of three hours — could hinder passengers as often as it helps them. He said planes that might be close to taking off could be forced back to gates, and passengers could wind up reboarding planes that have to go to the end of the takeoff line, causing further delays

"It's unfair to penalize the masses of air travelers because one person thinks there should be a government mandate to go back to the gate at a specific time," Castelveter said.

That argument made sense to Sandy Fortney, 54, of Philadelphia, a traveler who departed a plane at Chicago's O'Hare International Airport on Wednesday.

"If planes have to get out of lines on the tarmac and go back to terminals, they're going to be later than ever. People will end up missing connections in other cities," Fortney said.

DOT has been working separately on a rule that will require airlines and airports to have contingency plans. But federal rulemaking is a lengthy process, guaranteeing the issue will be among those waiting for the Obama administration.

Task force member Benjamin DeCosta, the aviation general manager of Hartsfield-Jackson Atlanta International Airport, said he favors time limits but they need to be tailored to each airline and each airport.

"This problem is so complex that one size doesn't fit all," DeCosta said.

The task force report recommends that:

• Airlines update passengers delayed on tarmacs every 15 minutes even if there is nothing new to report.

• A secure room be provided for passengers from diverted overseas flights so they can avoid having to go through security checks when reboarding an aircraft to their final destination.

• When practical, refreshments and entertainment should be made available to passengers confined aboard aircraft awaiting takeoff.

• Airlines should make reasonable efforts to be keep airplane restrooms usable.

The Transportation Department's inspector general last fall recommended setting a limit for how long airlines can force passengers to wait on planes that have been delayed taking off.

The 35-member task force was created in December by Transportation Secretary Peters to develop model plans after several incidents in which passengers were stuck for hours before their flight took off or before they were allowed to get off the plane.