Well I've never had to search for a website to find parking places for my elephant - he tends to create his own space!
Seriously though. Elephantparking would be a great domain name - memorable. Keyword domains are great for helping to get a good ranking in Google, but I would guess not very good for people to remember and go back. PPC is particularly good where, once people have found your site, they keep coming back, either because they bookmarked your site or just remember it.
So for me it depends on your business model. Is ppc viable? Is it so competitive that you have to pay too much per click to be viable? If so then you need to try to rank highly in search and keyword rich domain will obviously help.
It depends on how competitive your niche is - I would think airport parking is very competitive. So either you will need to do a lot of SEO and just having a good exact match domain name won't be enough, or you'll need to pay alot for ppc.
FWIW, I do have some airportparking pages on one of my sites. They are among my least visited pages!