The state Department of Transportation planned to repair a third crack overnight that was discovered on the approximately 50-year-old runway of Kona International Airport.

The first crack, of 3 by 10 inches, was discovered Monday afternoon and by 2:30 p.m. eroded into a hole 3 feet deep, said DOT Director Ed Sniffen.

Then a second crack in the runway was discovered running 8 inches long and 2 inches wide.

A crew from contractor Grace Pacific flew from Oahu to Hilo International Airport on Monday to make the repairs, forcing the airport to shut down the runway at 4:20 p.m. and disrupting 26 flights: nine trans-Pacific flights and 17 interisland flights. One plane was diverted and three interisland flights were canceled.

Some 160 passengers from diverted flights were booked into hotels, Gov. Josh Green said.

The work was finished at 3:30 a.m. Tuesday, and the runway reopened at 5 a.m.

The discovery of a third crack will require additional work scheduled for midnight to 3 a.m. Wednesday to avoid further flight disruptions. Sniffen did not describe the size of that crack.

Sniffen said Kona’s runway stretches over 11,100 feet, and Green said planes need at least 6,500 feet of runway to land.

Had the first two cracks appeared farther down the runway, planes could have avoided the cracks and landed, Green said.

Instead, Green said they appeared “smack dab in the middle” of the runway.

Green estimated that he’s flown 1,000 round trips into and out of Kona, where the area receives little rainfall but can suddenly be deluged by up to 2 inches of rain.

During Monday’s repairs, “layers” of water were discovered beneath the runway surface and likely undermined it, leading to the cracks, Sniffen said.

“It happens,” he said.

Green said that his phone was filled with calls and texts Monday from people asking about the airport and flight disruptions.

“Ed said, ‘I’ve got this. It’ll be fixed by 3 a.m.,’” Green said.

The state plans a $120 mil­- lion overhaul of the airport, which Green called “a moldy facility. … It needs support.”