Unsure how your private security firm makes money as the U.S. war in Afghanistan winds down? One option: Go into the drug trade – more specifically, the lucrative business of fighting narcotics. The State Department needs a business partner to keep its fleet of drug-hunting helicopters and planes flying worldwide. You could make up to $10 billion-with-a-B.

Starting next month in Melbourne, Florida, the State Department will solicit some defense-industry feedback on a contract to help operate its 412 aircraft, based in at least eight nations, before it reopens the contract for bidding. Among the missions the diplomatic corps needs fulfilled: "Provide pilots and operational support for drug interdiction missions such as crop spraying, and the transport of personnel and cargo," according to a pre-solicitation the department's bureau of International Narcotics and Law Enforcement Affairs released on Friday.

From its headquarters at Florida's Patrick Air Force Base, the State Department directs 51,000 annual hours worth of air operations. In Colombia, Bolivia, Peru, Pakistan, and Guatemala, it mostly performs "counternarcotics and law enforcement activities," explains State Department spokeswoman Pooja Jhunjhunwala, and in Afghanistan it does transportation support as well. Diplomats at the mega-embassy in Iraq also rely on State's contractor air fleet to move about the country. And in recent years, that fleet has also needed to perform short-term air missions in Sudan, Honduras, Malta, Libya and Egypt. Private-security giant DynCorp currently holds the contract for supporting the diplomatic fleet.

If you've got pilots and air-maintenance crews on your payroll, the risk of operating in "permissive and non-permissive" environments (i.e., dangerous places) could be worth your while. "The total dollar value of services could reach $10B over the life of the resulting contracts," the pre-solicitation reads. That's as much as State pays for its entire crew of mercenaries that protect diplomats worldwide.

The aviation contract covers more than just counternarcotics. State needs vendors for "personnel and cargo transport, aerial reconnaissance, medical and casualty evacuations, aerial herbicide application, aerial support to narcotics interdiction operations, aircraft ferrying, and emergent surge type operation." But the lion's share of missions have to do with stopping drugs. Of State's 412 aircraft, some 120 perform "drug interdiction and transport of personnel," and the remaining 292 are in some form of storage. DynCorp's website describes the mission as "help[ing] foreign governments improve their ability to develop and implement national strategies and programs to prevent the production, trafficking, and abuse of illicit drugs." (A company representative didn't say if DynCorp will seek to retain the revised aviation support contract.)

Without much publicity, the State Department has built a bespoke air force since the mid-1980s, one that's stacked with helicopters and heavily reliant on contractors. In the days before the U.S. military left Iraq, the diplomats who remain there solicited for a contract air force capable of the difficult, dangerous work of medical evacuation and search and rescue missions. A 2010 State Department inspector general report highlighted similar work performed in Pakistan – with an emphasis on crop eradication and interdiction – by DynCorp, one of State's longtime security contractors.

It's not just the State Department. One of the largest pots of security-contractor cash in the U.S. government, worth $3 billion, comes from an obscure Pentagon bureau called the Counter Narco-Terrorism Program Office (CNTPO), which disburses cash for missions that blend counternarcotics with counterterrorism. Among them: "airlift services the trans-Sahara," website support in Pakistan, and helicopter flight training in Mexico. Last month, CNTPO put out a contract to support counter-drug operations in Afghanistan beyond the 2014 date for ending the U.S. combat mission there.

But State won't look to dispense cash in Florida next month: its pre-solicitation vaguely alludes to awarding "a core operations contract" during the fiscal year that begins next October. In advance of assigning that aviation support contract, it's looking for feedback from potential vendors to help State "redefine its requirements to take advantage of modern aviation practices."

Doug Brooks, the president of the International Stability Operations Association, the professional association of security contractors, said he was unfamiliar with the State aviation effort. He cautioned that many aviation companies competing for these types of support-services contracts don't actually have much involvement in the private security business. DynCorp, however, does both private security and aviation support.

And some familiarity with security apparently helps. Among the tasks State wants handled for its counter-drug airfleet include "defensive security for air fields" and "reconnaissance missions when required," in addition to generic maintenance services and training foreign militaries in flight operations. The drug game is a dangerous trade, and so is maintaining a special air force for the American diplomats who try to contain it.