From AFI 65-601 Vol 1:

"9.10. O&M Minor Construction. Use O&M to cover projects whose funded cost is $750,000 or less. O&M funds may be used to fund a minor construction project costing between $750,000 and $1,500,000 if the project is justified to correct a deficiency that is life, health or safety threatening (10 U.S.C. 2805). If the project will cost more than $750,000, submit it to HQ USAF for further processing as either an unspecified minor construction or MILCON project. You must use MILCON major or unspecified minor construction to reimburse the O&M type construction funds for expenses incurred to that date. Reference AFI 32-1032, Planning and Programming Appropriated Funded Maintenance, Repair, and Minor Construction Projects."