Passengers departing Miami International Airport endured unusually long waits at security checkpoints Sunday, an indirect consequence of the partial U.S. federal government shutdown.

Since December 22, some 800,000 U.S. federal employees have been on mandatory leave or working without pay because U.S. President Donald Trump and Congress have been at an impasse over US$5.7 billion the president wants to build a wall on Mexico border.

Some employees, including the Transportation Security Administration (TSA) agents that staff airport security checkpoints, are considered "essential" and must work without pay.

Many however are apparently protesting by reporting sick at an abnormally high rate.

"We almost missed our flight. I wanted to eat a sandwich and now I can't. We're furious, this makes no sense," Italian Rocco Vincenzo, who was heading to the Cayman Islands before returning to his country, told AFP.

Vincenzo stood in a line of cranky travellers waiting to get through security to catch their flights that stretched the length of two city blocks.

"You want to travel? I'm going to stay in Italy and he (Trump) can stay in America," joked the 52-year-old labourer.

With about 40 TSA agents out, Miami International Airport officials decided Friday to close one of the airport's six terminals.

"Travelling in general is difficult, it's not pleasant, and this adds to the frustration," said Paul Reynolds, a 52-year-old Jamaican travelling to Kingston also waiting in line.

According to spokesman Greg Chin, the wait times at Miami International remain normal and the closed terminal will reopen on Monday, staffed by TSA agents.

TSA chief David Pekoske wrote on Friday that he had approved a $500 bonus for officers at checkpoints who have worked without pay in what is now the longest government shutdown in U.S. history.

"While I realize this is not what you are owed for your hard work," Pekoske tweeted, "I hope these actions alleviate some of the financial hardship many of you are facing."