Uhh...Bad coding practice to show up error to your customers. they all get scared with all that sh!t lol
there should be some error handler defined for this.
looks like there is a problem validating entry forms, my best guess is, it can't connect to Database due to heavy load.
Maybe you try some other time when load it less, else use other online booking websites.
Try
www.cleartrip.com. I use it for my Air travel Booking.