sentences:  60 airlines threatened to halt flights to Thailand if they were forced to move back to Don Muang airport.A two-week investigation led by Tortrakul Yomnak, a chief engineer for Airports of Thailand and prominent supporter of the anti-Thaksin movement, found that the runway was safe, and that cracks could be repaired in as little as a few hours.At the beginning of the investigation, Tortrakul had warned that the airport might need to be closed for three years.