Here’s something to keep in mind this busy travel season:

Airlines hit a record number of three-hour-plus tarmac delays in October. Even though that exceeds federal limits, no fines have been issued.

Jessica Arno, who lives in Greenville, S.C., knows about the delays firsthand. She ended up stuck on the tarmac for hours — a “really frustrating” experience that many passengers have encountered.

Despite the public outrage with airlines, it’s become clear that sometimes the blame for the delays lies with a number of entities besides the airlines, including airports, the Federal Aviation Administration, and U.S. Customs and Border Protection.

After an unexpected snowstorm led to the rash of delays in October, the FAA rushed to address the communication problems and other issues that led to the planes getting stuck on tarmacs for hours. And it felt a sense of urgency to act quickly.

“I’m not a forecaster, but I’m pretty sure that Mother Nature isn’t going to just sit idly by waiting for spring,” acting FAA chief Michael Huerta said in a speech this month.

The U.S. Department of Transportation said the October delays are under investigation. But the involvement of airports and other agencies in the web of factors that leads to the delays may make enforcement of fines tricky in some situations.

The DOT has authority to regulate airlines on consumer protection issues but doesn’t have the same authority over airports, DOT spokesman Bill Mosley said.

Meanwhile, regulators have levied only one fine for tarmac delays earlier this year, despite the dozens reported since the rule went into place more than a year and a half ago.

Most of the reported tarmac delays in the first year after the rule took effect were not violations, Mosley said. In some cases where the airlines “made a good-faith effort to return to the gate,” the DOT issued warning letters, while others fell under exceptions for reasons related to safety, security or air traffic control as permitted. The DOT said it is still investigating most tarmac delays since May.

“DOT probably should be imposing more fines in order to prevent these occurrences,” said Kate Hanni, founder of FlyersRights.org. “We’ve only seen one set of fines imposed, and I believe that that caused the airlines to relax a little bit.”

Arno said she feels “there’s so many loopholes the airlines can use. ... But it’s nothing to them to waste our time and money sitting on a plane for hours on end.”

The first penalty for tarmac delays was announced in November, when the DOT fined American Eagle Airlines $900,000 for 15 tarmac delays longer than three hours May 29 on flights arriving at Chicago O’Hare International Airport. Those delays affected a total of 608 passengers. A DOT investigation found that American Eagle, the regional carrier for American Airlines, was late in following its procedure to bring passengers back to the gate.

Atlanta-based Delta Air Lines has had some tarmac delays since the rule took effect, but it said every one was beyond the airline’s control because of weather or operational constraints.

During the first year after the rule took effect at the end of April 2010, the number of delays longer than three hours for each month ranged from zero to four.

The situation then deteriorated, with 16 tarmac delays lasting more than three hours in May and 14 such delays in June. After a few months of fewer incidents, along with an expansion of the rule to international flights at U.S. airports, there were a total of 18 tarmac delays that went over federal limits in October. That included 11 international flights that exceeded their four-hour limit.

All 18 delays were on Oct. 29, when a snowstorm fouled up airline travel in the Northeast, and all the flights were bound for either New York’s John F. Kennedy International Airport or Newark Liberty International Airport in New Jersey. Nearly all the delays involved diverted flights. They included three Delta flights — one from Atlanta to Newark that was diverted to Hartford, Conn., and was stuck on the tarmac for three hours and 20 minutes; as well as flights from Brussels and Madrid to New York that were diverted and ended up stuck on the tarmac for more than four hours.

Delta said it worked to provide food, water and working lavatories as federally required — including McDonald’s burgers in one instance.

Meanwhile, since the Oct. 29 incidents, the FAA has been working to improve the response of multiple organizations and federal agencies to prevent tarmac delays.

Among the issues airports and airlines have faced: more severe weather than expected, power outages, equipment outages, insufficient Customs staffing to process passengers arriving on diverted international flights, incomplete information and insufficient de-icing capabilities, according to industry observers.

On Tuesday, the FAA said its national command center in Warrenton, Va., will invite airports to join in teleconferences when diversions may develop, and it may open up a dedicated diversion information teleconference line for air traffic, other agencies, airports and airlines to exchange information. The FAA also said it “is taking immediate action” to improve communication to airlines and airports about equipment outages that may affect decisions to divert flights.

Delta spokesman Anthony Black said Delta has “a very good working relationship” with the airport and the FAA to reduce the number of flights affected by severe weather.

“We’re doing a better job because we’re getting more experienced dealing with it,” Black said. “Ultimately, some of the events occur because of things that continue to be beyond our control. Weather is the driving factor for those.”