We don't know. We have theorized that they had some sort of heat control or other chip that could control a spark. I don't know the brand or if they were hand-held, battery-operated ones. I do know it was a specific brand and the ME men specified they needed 15 of them before they "returned to Michigan."
Besides the cynical sorts we see posting on FR, the people who work in the stores involved were afraid to report if they had to identify themselves becasue they feared some sort of bad reaction from their employer. After being brought up to speed on the previously published reports of large phone buys, they realized this was something that might be important.
If you have ever spoken to an FBI agent, you know they just say "Thank you". Even in person, they give nothing away.
Maybe one of our FReepers would have some idea on the hair dryers. You cannot believe how much I wanted to ask someone over on the Terror Matrix thread, but I just felt this should not be publicized immediately.
I wonder if they would be used to melt some sort of solid to a liquid which could be used some how in a bomb in a liquid form. Do the planes have any 120volt outlets. Maybe they could mix a substance in with another substance and then hide the whole thing in some computer, head phones, etc. go back to the bathroom heat it up and kaboom, blow the whole plane up. You could hide a cream substance in practically any thing if you could form the substance in to shapes.
oh my mind is running wild now, hey you could strip the plug off of a hair dryer, strip the wires bare and then stick the wires in any type of outlet that would provide power, the wires heat up and kaboom, the substance would be in the hairdryer.
The hair dryer would be in the carry on luggage.