The Bradford sisters missing with their nine children were stopped from leaving the UK in March, ITV News has learned.
Their trip to Saudi Arabia was rebooked for May but there is no suggestion they were intending to travel to Syria at that time. Police are now trying to work out when the trip was planned.
The UK needs "a hotline" to Turkey so authorities can communicate more effectively when Britons who are suspected of attempting to cross over to Syria are missing, according to MP Keith Vaz.
Speaking after he met with the husbands of two of the three Bradford sisters who are feared to have travelled through Turkey to link up with terror group Islamic State, Vaz said Britain had to "sharpen up our act" in order to stop more people travelling to Syria.
The chairman of the Commons Home Affairs Committee said: "I still think we need to sharpen up our act as far as contacting the Turkish authorities are concerned. Turkey has always been very responsive but there's still this desire to send emails. Well, you know, you can't.
"We are dealing now with life-and-death situations where you have to pick up a phone, a hotline, between the United Kingdom and Istanbul and tell the authorities that people are missing, get photographs to them as soon as possible, because this repeats a pattern that we've seen before with Bethnal Green and the three young girls there."
Vaz is due to meet with police tomorrow to discuss the Bradford sisters' case after their family accused police of being "complicit in the grooming and radicalising" of the women.
Speaking from Pakistan, one of the husbands of the missing Bradford thought to be heading to Syria has told ITV News of his worry.
Here's what we know about the Bradford family of 12 who are feared to be travelling to Syria.