The M39 ALG is an inexpensive addition to the UNSC arsenal. The first craft of this type, the M37 UCAV, was introduced in 2540 in the Human-Covenant War. However, these were fairly bulky and slower. They were also less cost-effective overall. The M37 was phased out of service in 2550-'52, along with multiple other various pieces of equipment, to help finance the expensive SPARTAN program. However, the idea of an unmanned infantry aid was not forgotten, and in 2562, the niche was once again filled by the M39. Capable of speeds up to 71 miles per hour in 1-G evnironments, the new model proved much more effective. As the years of service progressed for the M39, modifications were added, such as the modification allowing the M39 to be controlled by an A.I. and not remotely by a human operator, which was introduced in 2577. Improvements like this allowed the M39 to stay in service until the mid-27th century.