It's round three of mailings that claim to be from US Airlines. There is no US Airlines so don't be drawn into the free ticket offer.
Another letter appears to be from popular, online, discount travel web site Travelocity. It promises plane tickets and a 2-night stay at well-known hotel chairs.
Travelocity says not only is this not a real offer from but they're pursuing legal action against the sender.
One of the offers comes with a return address sticker not even trying to appear to be a legitimate company rather claiming to come from an individual in Florida.
You're always better off going through a real company's web site, or switchboard, looking for good deals rather than replying to too-good-to-be-true offers that land in your mailbox, inbox or fax machine.