Brandishing a knife, he threatens the two women staff before making off with an undisclosed amount of cash.
The robbery in Luton came six weeks after a similar incident in nearby Dunstable and, this week, a £150,000 raid on a jeweller's in Banbury, Oxfordshire.
Police are investigating the possibility the crimes are linked.
The first incident happened on July 7 - the fourth anniversary of the 2005 terrorist bombings in London.
A man in a burkha, which left only his eyes visible, walked into First Choice Travel in Dunstable. After threatening two women staff he took the cash and escaped through the back door at 10.15am.
On August 16, a burkha-clad man made off with a 'large amount of cash' from the Thomson travel shop in Luton.
Then, on Tuesday, a man wearing a burkha and two accomplices, who wore dark clothes and had their faces covered, stole £150,000-worth of Rolex, Cartier and Breitling watches from jeweller Michael Jones in Banbury.
They threatened four members of staff with a knife and an axe at 2.30pm before escaping in a black Audi estate driven by a fourth man. The car was found abandoned. The robbers are believed to be Asian.
Bedfordshire Police said they were 'keeping an open mind' about whether the crimes were linked. They want to trace two women who went into the Thomson shop in Luton during the robbery but left because staff had been told to say it was closed.
Thames Valley Police, which covers Banbury, refused to deny the incidents involved the same man.
Detective Inspector Steve Duffy said: 'Thankfully nobody was injured during the robbery but obviously staff have been left very shaken by what happened.'
There have been growing concerns over the use of burkhas and other Muslim clothing to conceal criminals' identities.
Somali Mustaf Jama, one of the armed gang that shot dead PC Sharon Beshenivsky in Bradford, reportedly escaped from Britain after hiding his face behind a traditional Muslim woman's niqab and using his sister's passport.
And a man and woman made off with £200,000 of jewellery from a London store in 2002 after concealing their identities with burkhas.