ABOUT 22,000 unmarried military personnel will lose their annual free flights home because of Budget cuts aimed at boosting the Government's surplus.

The benefit has been in place for decades and allows unmarried Defence members based in places far from home, such as Darwin or Townsville, to be reunited with their family at Christmas.

Navy sailors received two flights and trainees three. They have now been cut to one only for under-21s.

About 27,000 Australian Defence Force members are single and about 5000 of those are under 21. Married troops posted away from families are entitled to six free reunion flights a year. That benefit is also under review.

Defence chief General David Hurley yesterday confirmed all allowances and entitlements were under review, but he was not aware of any change to the married reunion travel.

He argued the free airfare for older single people was outdated. He said it was in place when he joined the army 40 years ago when salaries were low and airfares were very expensive from such places as Townsville.

"The world's changed since that was introduced. You get cheaper airfares, communications are different the town is not so isolated any more," General Hurley said.

"Do we really need to subsidise 30 or 40-year-olds for a trip home each year?"

One soldier said airfares might be cheap on a general's salary, but the cut was another example of picking the low-hanging fruit. He said it smacked of discrimination as married members received six free flights a year.

Defence funding was cut by $5.5 billion in the Budget and it is estimated the unmarried travel cut will save just $15 million a year - or $681 for each single member over 21 - from this July 1.

General Hurley also revealed the number of senior military officers, which has grown by 70 per cent in recent years, would be cut by a dozen jobs when the Afghanistan mission was over in 2014. Australian Strategic Policy budget expert Mark Thomson released his annual defence budget analysis yesterday showing personnel costs for Defence stand at $10.4 billion a year.