The FAA says a single-engine Beechcraft Bonanza A36 crashed near the end of the runway at the airport around 6:15 p.m.
Suffolk County police say the small plane took off in the southwest direction and, according to a witness, was airborne and for some "unknown reason" attempted to return to the airport. Upon return, the aircraft crashed.
They say two adult men, the pilot and a passenger, were pronounced dead at the scene. They have yet to be identified.
No other injuries were reported.
It's not clear yet where the plane was headed or the purpose of the flight.
Doing a 180-degree turn shortly after takeoff is considered extremely risky for a single-engine plane, according to FAA guidance. If engine failure is to blame, pilots are told to try to land the plane without turning. But it's not clear what, if any, mechanical trouble was discovered or communicated.
The FAA and NTSB both responded to the scene, and are investigating.
The Suffolk County Police Department is also processing the crash with a crime scene investigation team, like it would with a fatal car crash.
Islip officials say the runway will remain closed while the investigation continues. They ask passengers to check with their airline for any possible delays or cancellations.
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