SEPANG, Malaysia — The radar blip that was Malaysia Airlines Flight 370 did a wide U-turn over the Gulf of Thailand and then began moving inexorably past at least three military radar arrays as it traversed northern Malaysia, even flying high over one of the country’s biggest cities before heading out over the Strait of Malacca.

Yet inside a Malaysian Air Force control room on the country’s west coast, where American-made F-18s and F-5 fighters stood at a high level of readiness for emergencies exactly like the one unfolding in the early morning of March 8, a four-person air defense radar crew did nothing about the unauthorized flight. “The watch team never noticed the blip,” said a person with detailed knowledge of the investigation into Flight 370. “It was as though the airspace was his.”

It was not the first and certainly not the last in a long series of errors by the Malaysian government that has made the geographically vast and technologically complex task of finding the $50 million Malaysia Airlines jet far more difficult.

A week after the plane disappeared, the trail is even colder as the search now sprawls from the snowy peaks of the Himalayas to the empty expanses of the southern Indian Ocean. Nobody knows yet whether the delays cost the lives of any of the 239 people who boarded the flight to Beijing at Kuala Lumpur’s ultramodern airport here. But the mistakes have accumulated at a remarkable pace.