A Ryanair-operated Boeing 737-800 was forced to return to Thessaloniki, Greece, shortly after takeoff on Friday after a cabin window became dislodged during the climb, triggering rapid cabin decompression and a major in-flight emergency.

What is confirmed is that the aircraft landed safely, one passenger required medical treatment, and an official investigation into the cause is underway.

The aircraft had departed Thessaloniki for Memmingen, Germany, before the incident occurred.

Witnesses said a loud explosion-like noise was heard while the aircraft was climbing, followed almost immediately by the loss of cabin pressure.

Oxygen masks deployed automatically as the pilots initiated an emergency descent and turned the aircraft back toward its departure airport.

The passenger seated next to the damaged window, identified in multiple reports as a sixty-one-year-old Serbian man, was partially forced through the opening.

Witnesses said his head, neck and shoulders extended outside the aircraft while his seat belt prevented him from being completely ejected.

His wife reportedly held onto his legs while nearby passengers and several medically trained travelers helped pull him back into the cabin.

The man suffered neck injuries, abrasions and friction burns but remained conscious after the aircraft landed.

A pregnant passenger was also taken to hospital as a precaution and was later discharged.

Passengers described scenes of panic inside the cabin.

One said the sound resembled a tire exploding, followed by screaming as the aircraft rapidly lost altitude because of the decompression.

Another said the cabin crew appeared overwhelmed while everyone immediately put on oxygen masks.

Witnesses added that several passengers rushed forward to help the injured man, whose seat belt is widely credited with preventing a fatal outcome.

Ryanair confirmed that the flight returned to Thessaloniki after a passenger window became dislodged during flight.

The airline said the aircraft landed normally, passengers returned to the terminal, one passenger requested and received medical assistance on the ground, and a replacement aircraft later completed the journey to Germany.

The cause of the window failure has not yet been established.

Some early reports suggested that debris from the aircraft's right engine may have struck the window after an apparent engine malfunction.

What is confirmed is that investigators are examining the sequence of events.

The reported engine-debris scenario has not been officially confirmed.

The investigation is being led by North Macedonia's Aircraft Accident and Incident Investigation Committee, while the United States National Transportation Safety Board has been notified because the event involved an engine issue and cabin decompression.