A commercial jet plunged from the clear blue sky minutes after takeoff in Ethiopia on Sunday, killing all 157 people on board, including eight Americans.

The veteran pilot of doomed Ethiopian Airlines Flt. 302 issued a distress call as the craft — a practically new Boeing 737-8 MAX — wildly gained and lost altitude before smashing into the ground 6 minutes after take-off, leaving behind little more than a smouldering crater of twisted metal.

It was the second time a 737-8 MAX had been involved in a death plunge, killing all aboard, in just five months.

“The blast and the fire were so strong that we couldn’t get near it — everything is burnt down,’’ witness Bekele Gutema told the BBC of the Ethiopian crash site.

A photo posted by the airline showed its CEO picking a piece of gnarled metal from the debris-strewn impact crater — as authorities and Red Cross volunteers used bulldozers to scour for human remains amid mangled personal belongings such as sneakers, laptops and water bottles.

The plane took off from Bole International Airport in Addis Ababa en route to Nairobi, Kenya, at 8:38 a.m. local time for what was supposed to be a routine two-hour shuttle between the busy capitals.

Pilot Capt. Yared Getachew, who had more than 8,000 hours of flight time, reported “difficulties” to air-traffic controllers almost immediately.

The sky was clear, and the winds topped out at a gentle 11 mph, according to the flight-tracking service Flightradar24 — yet the plane’s altitude began dangerously fluctuating.

Its vertical speed went from 0 feet per minute to 1,472 to minus 1,920 at various times and at one point dropped 450 feet in just 22 seconds recovering altitude, flight data shows.

The fluctuations in altitude mirrored issues encountered by the other fatal Boeing 737-8 MAX that crashed in October, although experts were quick to warn that it is too early to say whether the planes’ issues were the same.

Getachew had been cleared to return to the Ethiopian capital but then lost radio contact at 8:44 a.m., and the doomed flight came crashing down moments later.

The victims were from at least 35 nations and included eight unidentified Americans.

“The US Department of State extends our condolences to all who are impacted by the tragic crash this morning of Ethiopian Airlines flight ET302. We can confirm the victims include US citizens,” the agency said in a statement.

“Out of respect for the privacy of the families, we won’t have any additional comments about the victims.”

Nineteen victims were employees of the UN or affiliated organizations, and many were traveling to Nairobi for the UN Environment Assembly that begins Monday there.

Relatives of those feared aboard the flight gathered at the Kenyan airport, anxious and tearful.

“I came to the airport to receive my brother, but I have been told there is a problem,” Agnes Muilu said. “I just pray that he is safe or he was not on it.”

The state-owned airline said it will investigate the crash along with the Ethiopian Civil Aviation Authority, the Ethiopian Transport Authority and Boeing.

The US National Transportation Safety Board has sent a team of four investigators to aid the probe, officials said.

The Federal Aviation Administration said it also planned to assist.

Experts said the airline is known for its stellar safety record.

“It’s one of those airlines that when you have worries about any other, you always say, ‘I’ll take Ethiopian,’ ” said CNN aviation expert Richard Quest.

In a statement, Boeing said it is “deeply saddened” by the crash and that it will “provide technical assistance” to investigators.

With Post Wires