RAF Valley jobs on Anglesey could be relocated to RAF Leeming in Yorkshire according to union officials.
Unite claims there is an "active proposal" from the Ministry of Defence to move all the Hawk T1 depth maintenance from Wales to RAF Leeming by 2023.
They say this could see up to 70 jobs relocated in a blow to Anglesey but a boost for the Yorkshire airbase.
The union claimed there was a political element to the move with RAF Leeming in the Richmond constituency of chancellor Rishi Sunak, who had been unsuccessfully pressing to bring the Red Arrows' Hawk T1 team to the base.
They said in the long term there are another 100 roles at risk with the Hawk T2 contract under discussion with MoD and BAE Systems.
The Hawk T2 is used for fast jet fighter training and has replaced the T1 at RAF Valley over the last few years - although the T1 is due to remain in service until 2030.
100 Squadron, based at RAF Leeming, now fly the Hawk T1 in the ‘aggressor’ role, simulating enemy forces and providing essential training to the RAF front-line units.
The MoD said under 'Hawk 2020' there is a plan to replace the existing support contracts for the Hawk T1 and T2 aircraft into a new support contract to run from the end of 2020, when the current contracts expire, for the next 13 year period.
Most Read
They added that no decisions have been made and it is too early to speculate on any potential impact on the workforce. Around 400 people are employed on Hawk contracts at RAF Valley.
Peter Hughes, Unite Regional Secretary for Wales, said: “Unite are alarmed at the proposals presented to our representatives that could slash the number of jobs on the Hawk contract by 2033, with many of the job cuts potentially coming in the next five years.
"Anglesey has suffered a significant loss of skilled work recent years and the prospect of the further loss of aviation jobs at RAF Valley must be reversed otherwise the economic damage will be another hammer blow to the area.
"The rationale for moving the T1 Hawk work to RAF Leeming does not add up, especially as the MoD are seeking significant efficiency savings as part of the new contract.
"Chancellor Rishi Sunak needs to keep his hands off our member’s jobs at RAF Valley."
While Mr Sunak has campaigned to bring the Red Arrows to RAF Leeming he has not publicly commented on other Hawk jet jobs.
Mr Hughes added: "As the contract negotiations between the MoD and BAE Systems have recently been put on temporary pause the job cuts are not a done deal but there is still a significant threat to overall job number at RAF Valley in the coming years.
Don’t miss
"Unite will campaign to save the jobs under threat at RAF Valley. We believe these are the wrong proposals at the wrong time and for the wrong reasons.
"The MoD should be investing in the RAF Valley workforce for the long term rather than looking to cut jobs."
Ynys Mon MP Virginia Crosbie said: "I have spoken with the MoD to address the concerns of my constituents here on Anglesey and I understand that they are in discussion with BAE Systems regarding the potential future support options for the Hawk training aircraft.
"However, these are routine discussions and both parties are committed to ongoing dialogue with local employees and their representatives.
"I will continue to liaise with the MoD to ensure that the views of my constituents are taken into account in any future decisions."
An MoD spokesman said: "As part of routine business the MOD is in discussion with BAE Systems to determine potential future support options for the Hawk.
"Both the MoD and BAES remain committed to ongoing dialogue with our employees and their representatives."
The MoD added that it had continued to invest in RAF Valley, with the recent arrival of Texan aircraft offering further engineering opportunity at the site.
The office of Rishi Sunak has been asked to comment.