The long-awaited boost for alien hunters follows years of campaigning by the British disclosure movement, who want all world Governments to release all their alien files.
UFO researchers, backed by a House of Lords peer, have been fighting for the release of 18 top secret Ministry of Defence (MoD) files about UFO sightings from more than 30 years ago.
The Government faced claims of a cover-up from conspiracy theorists when their release was stalled at the end of 2013.
Some investigators claim the files could provide key evidence of extra-terrestrial life visiting the UK and of specific information about famous controversial sightings such as the Rendlesham Forest incident - a series of reported sightings of unexplained lights and the alleged landing of one or more craft in Suffolk in late December 1980.
Lord Black of Brentwood, who asked the Government for an update through a Parliamentary question last summer, was assured the files would be released by the MoD to the National Archives by March this year.
Alien hunters are confident these records could prove if extra-terrestrial life actually exists, as these were the most secretive files held in the private offices of various Cabinet ministers.
Although the files are being released to the National Archives, it is not yet clear when they will be available for public inspection.
This is because the archive organisation can set its own release date.
In his Parliamentary question, Lord Black asked: "What is the latest estimate of when the 18 files will be passed to the National Archives, and then released to the public."
Defence Minister Earl Howe replied: "The latest estimate of when the 18 files will be delivered to the National Archives is before March 2016.
"The National Archives will make the necessary judgement about when they release these files to the public."
A number of older UFO files held by the UK government have already been released, including details of sightings by officials and police.
Nick Pope, who used to investigate the existence of UFOs for the MoD, said the files should contain some fascinating sightings.
However, referring to what is often called the most famous UFO claim in history - sparked by claims an alien spaceship crashed in New Mexico, US, in 1947 - Mr Pope added the soon-to-be-released files are probably not a "UK Roswell-style UFO in a hangar style cover up".
When the release of the files were stalled in 2014, which the MoD blamed on "additional processing requirements", Mr Pope sympathised with alien researchers.
He said at the time: "This massive delay will have conspiracy theorists up in arms. It looks like the MoD is stalling.
"The suspicion will be that there's a bombshell in these files and that the Ministry does not know how to handle it.
"I can understand why conspiracy theorists will be angry and suspicious."
Mr Pope worked at the MoD for 21 years, but was specifically assigned to investigate UFOs for a three-year period.
He said: "Having worked on the MoD's UFO project I'm sorry to say that we don't have any crashed spaceships hidden away in some RAF hangar, as some believe, but we do have some fascinating and unexplained cases in our files."
The 'Redlesham Forest incident', which is alleged to have taken place near RAF Woodbridge, Suffolk, in 1980, saw US Airman First Class John Burroughs, who was stationed there, exposed to radiation after a mystery "UFO visitation".
He has since won damages from the American military, but still wants answers about what happened and hopes they will be in the new files.
Pat Frascogna, his lawyer, said: "We know there is information contained in these MoD files about the Rendlesham Forest incident because the MoD clearly indicated so in responding to a Freedom of Information request by John Burroughs last year."
