A Canadian-registered air ambulance jet carrying six people plummeted thousands of feet in three minutes and vanished off the Massachusetts coast early Saturday — the latest reminder that the medical transport system ordinary Americans count on in their worst moments operates on margins thinner than anyone wants to admit.

The Gulfstream G-100, operated by Latitude Air Ambulance of Hamilton, Ontario, lost contact with the FAA at roughly 1:20 a.m. while flying from Bermuda to Boston Logan International Airport, according to an FAA statement. FlightAware data cited by the New York Post shows the aircraft dropped from 23,500 feet to 11,000 feet in just three minutes starting at 1:04 a.m. — a descent rate that demands an explanation.

Air traffic control audio obtained by NBC News captures a controller asking the pilot,