Speaking at an unrelated press conference at the Bronx Zoo on Thursday, Sept. 18, 2014. View Full Caption DNAinfo/Jeff Mays

NEW YORK CITY — Notoriously late Mayor Bill de Blasio kept more than 100 people waiting at the gate to board a JetBlue flight from JFK Airport to Puerto Rico last month because he was running late and had the plane held for him, DNAinfo New York has learned.

The passengers — including state Comptroller Thomas DiNapoli, City Council Speaker Melissa Mark-Viverito and numerous other lawmakers as well as vacationers — were forced to cool their heels for roughly 20 minutes on Nov. 6 as they waited to board JetBlue Flight #703 for San Juan, where the Somos El Futuro Fall 2014 Conference was being held.

“We started to make our way over to the gate, about a half-hour before the flight was due to board,” a passenger recalled.

“There was a long line, but there was no boarding call and no one knew why. We were saying, ‘Why are we just standing here? The plane is here. We are here. So what's the holdup?'”

Planes generally begin boarding 30 minutes before scheduled departure. After waiting roughly 20 minutes — nearly 10 minutes before they were due to leave — activity near the security entrance caught their attention.

It was de Blasio and a small entourage of aides, mostly NYPD bodyguards, walking briskly toward them.

“We finally understood why. It was the mayor that was holding us up, of course, and a few people could be heard joking, ‘Late again,'” the passenger said.

"He was walking quite fast, with four or five people, probably security people, and he went straight past everyone onto the plane.”

It is unclear why the mayor was late for the plane, but his NYPD security personnel had to radio the airline security to hold it for him, sources said.

The witness said the mayor and his security personnel were seated first, and then the rest of the passengers were allowed to board the plane.

An industry source explained that flights are often held for dignitaries as a “courtesy.” And with the mayor it is easier to have his detectives sweep the cabin without passengers aboard.

Earlier that day, the mayor attended a 45-minute press conference in Coney Island where he, Sen. Charles Schumer and numerous federal and city officials announced that city hospitals would receive at least $1.6 billion in Federal Emergency Management Agency funds to repair damage from Hurricane Sandy.

That press conference started around 11:25 and ended shortly after noon. His plane was scheduled to leave at 1:52 p.m.

A spokesman for de Blasio did not return an email seeking comment.

Five days after the JetBlue holdup, the mayor missed a memorial ceremony honoring the hundreds of victims of Flight 587, which crashed in the Rockaways on Nov. 11, 2001.

“On the Inside” previously reported that on that morning the mayor was 30 minutes late catching an NYPD boat waiting for him at Gracie Mansion to take him to the event.

His handlers initially blamed the delay on morning fog, even though NYPD boats have sophisticated radar that allows them to navigate through “pea soup.

The mayor eventually clarified why he was late, saying he had a "rough night" and should have gotten moving earlier in the morning.

Since then, de Blasio has kept a vow to be on time for public events.