Up to 7,000 people have taken part in a march and rally in support of the RAF base at Lossiemouth in Moray.
Scotland's First Minister Alex Salmond and the leaders of the other three main parties at Holyrood were among those attending.
It is thought the base could be closed as part of the government's strategic defence review.
Actor Ewan McGregor has backed the campaign. His brother Colin used to be based at Lossiemouth.
The Star Wars actor said closing it would "devastate" the local community.
It is feared the base's Tornados may move to RAF Marham in Norfolk.
The march went through Lossiemouth and ended with a rally at Grant Park football ground.
The Ministry of Defence has said no decision has been reached about RAF Lossiemouth's future.
However, Defence Secretary Liam Fox told Sky News that using Lossiemouth as an army base may be an option.
He said: "We have said we are going to have to lose some types of assets but we will be bringing the Army back from Germany and we have to put them somewhere."
He said the issue of basing would be looked at over the next six months.
"We will take into that the regional implications where we have got Kinloss and Lossiemouth very close together. Clearly there is a much bigger regional impact there," he added.
The campaign to secure the future of Lossiemouth comes amid fears for Moray's other RAF base at Kinloss, after the UK government announced it was cancelling the next generation of Nimrod reconnaissance aircraft, which would have been stationed there.
Crieff-born McGregor said the closure of both bases would devastate Moray's close-knit community and have far-reaching effects.
His brother Colin was a former Tornado pilot, based at Lossiemouth.
"I was shocked to hear the recent news that RAF Lossiemouth is under threat due to the possible relocation of Tornados to RAF Marham," he said.
"I had the privilege to fly from RAF Lossiemouth in the back of a Tornado piloted by my brother Colin.
"It was evident to me that Lossiemouth and the Highlands offer the very best training environment for Tornado crews who continue to be the RAF's front line in Afghanistan.
"The closure of both Kinloss and Lossiemouth would be devastating to this close-knit community and the effects would be far-reaching."
First Minister Alex Salmond said he intended to make the UK government "sit up and listen" to the people of Moray and Scotland.
"It is obvious that the Westminster government must do more to support the most defence dependent community in the UK in its hour of need," he said.
"This goes far beyond Moray. It is a national issue of national importance to Scotland."
Highlands and Islands Enterprise said RAF Kinloss supported 2,341 jobs on the base and in the wider community, and contributed £68m a year to the local economy
The base at Lossiemouth supports a further 3,370 jobs and contributes £90.3m annually. It is home to four squadrons flying the Tornado, which is the UK's primary ground attack aircraft.