Back in 2012 Ebay started a partnership with Gogo company — the inflight wifi provider. This partnership granted a free access to eBay.com for customers on Virgin America and Delta flights.
As you can understand, this is a very smart move. Ebay got attention of hundreds of thousands potential customers that are bored during their flights.
Such co-marketing campaigns is a real gold to many young companies, as you can get tons of new visitors or customers at a low or even no cost at all (if your product gives a great additional value to a bigger company).