I recently completed a rental analysis for my local airport, to help them determine market rent for their hangars and some office space. I found rents by surveying similar-sized airports in nearby counties. I actually found a lot more rents than sales of owned hangars, as hangars don't tend to sell very often, but that probably varies by location. You should call up the airport managers at nearby airports and ask about hangar sales and rents. Unlike major airports, it's usually fairly easy to get ahold of managers at general aviation airports. Many are reluctant to divulge much information, though.
Just be careful about whether rents are ground rents or building rents. I've seen corporate hangars rented both ways.
As for the cost approach, be careful. In my market, hangars often aren't worth what they cost to build (based on rents and sale prices). They are built for personal or corporate use and have more value to the owner than to buyers. Many corporate owners/builders really spend a bunch of money making them nice (including office space, lounges, meeting rooms, locker rooms, etc.), but some buyers probably don't want to pay that much. Or, perhaps I should say the "right" buyer would, but many would not.
The same caveat applies to the income approach. I found that hangar rents in my location aren't generally high enough to support market-based construction. Again, specific users are willing to pay above-market rent for a new hangar if they really want one, but existing hangars rent for rates that are too low to support construction. This will vary by location, of course, but be aware to look out for it. The airport may go ahead with construction anyway, because they are not only looking at hangar rent, they are looking at increased airport usage, which translates to more landing fees, more fuel sales, more maintenance and repair, more restaurant sales, etc. From the airport manager's perspective, it seems to all come down to airport use, fees and revenue, not just hangar rents.
Look on
www.hangartrader.com,
www.hangarnetwork.com,
www.barnstormers.com and loopnet for listings and leads on sales.
As Terrel mentions, with sales you will almost certainly be looking at leasehold value (airports don't like to sell airside parcels). You have to factor in the ground rent into your analysis and valuation.
