The agreement comes after a year-long industrial battle for ground crew that led to a fresh round of strikes last month, forcing the airline to ground 48 flights across Australia.

Jetstar says the deal includes a 12 per cent pay rise over four years and improvements to rostering and allowances.

However, the Transport Workers Union accused the company of blackmailing low paid workers to vote up the deal or not receive rate increases owed from March 2019.

"For low-paid workers, the prospect of being denied money from a rate increase that was due a year ago was too much," national secretary, Michael Kaine, said.

"The lack of hours these workers struggle with means many live pay check to pay check.

"Jetstar knows this and therefore chose to force this deal on workers using disgraceful blackmail tactics."

Jetstar said backpay to when the previous agreement expired in March last year was not a right but a negotiated benefit.

Workers were given the chance to secure it and did, it added.

"We're pleased our ground crew have said yes to this deal, which gives them a 12 per cent pay increase over four years as well as improvements to rostering and allowances," a Jetstar spokesman said.

"This agreement rewards our people with a wage deal that is almost double the inflation rate but still lets us deliver the low fares our customers expect."

Workers first held strikes in December last year after the union accused the airline of proposing an agreement "designed to keep Jetstar workers impoverished".

The union also lashed the federal government for failing to hold airports and airlines to account over underemployment and low wages in aviation, saying thousands of workers across airports are underemployed, some on as few as 60 hours per month.

Australian Associated Press