After thousands of delays at one of America's biggest airports, beleaguered travelers ask – how?

Runway construction at one of America’s largest airports led to runaway chaos this week, with travelers stranded and flights around the country going into San Francisco delayed or canceled.

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Thousands of flights departing or heading toward San Francisco international airport had been delayed or canceled since construction began on Saturday, raising questions about how the airport and the airlines prepared, or failed to prepare, for a possible calamity.

Airport officials said they alerted airlines about the construction months ago, but it is up to the individual airlines to decide if they are willing to make reductions to their flight schedules. Some cut flights by just 10%.

“The frustrating part was not being notified of potential delays prior to our trip since this runway closure was scheduled and planned,” said Chi-Lan Tran, whose trip back from Detroit took nine hours on Sunday. “Airlines knew about this.”

Numerous other travelers voiced their frustration about lengthy delays and lack of communication from airlines.

The runway in question is one of the most heavily-traveled at the airport, with more than 68% of all flights crossing at the runway intersection. All airlines use this runway, said Doug Yakel, an airport spokesman.

The airport had warned the airlines of the impending and much-needed construction for months, Yakel said.

“The most fundamental thing here is that flight schedule reductions are voluntary,” Yakel said. “We presented this closure to the airlines, asked them to look at their schedules and opportunities to reduce, and they came back with what reductions they were willing to make. It all comes down to an airline business decision.”

The airport was able to reduce all flight schedules in total by 13%, Yakel said, but that clearly wasn’t enough. Since Saturday, there have been more than 2,000 flight delays and more than 600 flight cancellations out of San Francisco, according to the tracking site FlightAware.

United, which has a hub in San Francisco, reduced its flight schedule by 10%, while American Airlines reduced its flight schedule by 15%, according to representatives from both airlines. Delta reduced its flight schedule by 10%.

“We knew there would be delays but that they would be less severe than if airlines had attempted to run a full flight schedule,” Yakel said. “I would also add that airlines could choose to make no reductions and you would see greater delays and more day-of cancelations.”

Danny Page, whose American Airlines flight coming out of a layover in Dallas-Fort Worth was delayed on Monday for four hours, said airlines should have alerted travelers when they were booking their tickets that this runway closure was going to happen.

“If I had known in advance, I would have switched my flight to arrive in Oakland or another Bay Area airport,” he said. “I can deal with maintenance delays or weather, but it seems like more should have been done to let travelers know in the run up to this project.”

Keith Kurmon spent four hours on Sunday crowded at a gate at Boston’s Logan international airport, waiting to get back to San Francisco along with dozens of others. He whiled away the time by reading and watching The Great British Bake Off to remain calm in the chaos, and tried to conserve the battery life on his phone as others jostled for the few outlets that were there.

“The attendants at the desk tried to give as much information and updates as possible, but when it’s backed up that much at SFO, it’s hard to say anything other than ‘we’ll know when we’re on the plane’,” he said.

He heads to New York later this month, and is nervous about a repeat experience – construction is slated to continue until 27 September. Fortunately, construction appears to be ahead of schedule.