Craig McCaw, for instance, is more recently known for running Clearwire, the WiMax-loving broadband provider that Sprint acquired in 2013. Ian Small, meanwhile, headed up key technology development at international carrier Telefonica and is currently the CEO of Evernote. Marni Walden is the one with the most recent telecom experience -- she was an Executive VP and President at Engadget's parent company, Verizon, where she managed Global Media and New Business.
These are only the "founding members," so don't be shocked if more people join the ranks. It might need to expand given Loon's focus on providing internet access to remote or underserved areas. The current board includes people from American and European providers. It might want advisors who are particularly familiar with developing countries and other places where broadband is scarce or non-existent.