Some more information from a reliable source:
"Brazil’s aviation authority, ANAC, said Tuesday morning that the LaMia airline had asked permission to fly directly from Brazil to Colombia, but the request was denied on the basis of international aviation agreements. An ANAC spokesman said under these agreements a charter flight between two countries can’t be operated by an airline from a third country."
Plane Carrying Brazilian Soccer Team Crashes in Colombia; At Least 70 Killed - WSJ