-- Airline emergencies that leave people stranded on tarmacs for hours can happen for a simple reason: There aren't buses available to ferry passengers off the stranded plane and take them to the nearest gate.
The massive delays, such as one that occurred over the weekend in Hartford, Conn., during a snowstorm, underscore a need for airlines and airports to have better plans in place to fetch passengers off planes, according to aviation experts and consultants.
Erwin Zimmerman, vice president of Cobus Industries, which sold scores of large airport buses to 15 airports nationwide, said the Federal Aviation Administration provides funding for airports to buy buses. But buses are often low among airport priorities.
"Airports should be ready, willing and able to get people off that airplane," Zimmerman said. "Unfortunately, I don't believe that there are any rules or requirements that the airports have that equipment in place."
Even with plans in place, things can still go wrong. For instance, when handled smoothly, Pittsburgh's airport can receive 18 extra flights from shuttered East Coast airports and send planes to empty gates or rotate them among crowded gates before parking them empty.
"We're their port in the storm," said Stephanie Saracco, chief of operations for Allegheny County Airport Authority, which developed its plan in 2009.
But when emergency plans are inadequate or overwhelmed, passengers get stranded on planes without food or toilets.
"One issue is how often does this happen and how well is it integrated into your regular planning?" said Richard Marchi, a senior adviser at the Airports Council International-North America. "The airports they don't serve very much, that's where the problems come."
Hartford, which has only 22 gates, got 23 diverted flights from the New York area and had to cope with falling snow and intermittent power failures. JetBlue, which had six diversions, typically has only four arrivals and four departures a day at Hartford.
Most diverted planes are able to quickly fly again and get passengers on their way. But then the airline temptation is to keep passengers aboard the plane, even if the wait runs so long that crews are no longer allowed to fly, as happened in Hartford.
"That's an airline business decision, not an airport decision," said Joshua Schank, president of Eno Transportation Foundation. "If they wanted to, they could have found a way to get the people into a place where they wouldn't have to wait without food, water or bathrooms."
Larger airports have buses that can each ferry more than 100 passengers each between terminals. But smaller airports might not have those buses — or commercial drivers trained on routes among the runways.
"There are safety concerns about having buses crossing active runways, particularly in snowstorms," said Bill Mosley, a Transportation Department spokesman.