Traditionally, most people join the U.S. military in their late teens or early to mid-twenties. As of 2013, the average enlistment age for people joining the Army was 20.7 years. Each of the four military service branches and the Coast Guard also have their own maximum age standards for enlistment or officer commissioning. So while the maximum military enlistment age set by Congress is 42 years, if you're 35 or older you might have a tougher time trying to enlist.

Maximum Enlistment Ages

The military services and the Coast Guard are allowed by Congress to set their own particular maximum enlistment and officer commissioning ages. The Air Force has the lowest maximum enlistment age at 27 years, though officer maximum commissioning age varies by career field. The Navy's maximum enlistment age is 34 years, with varying officer commissioning ages as well. The Marine Corps sets its maximum enlistment and officer commissioning age at 28 years, though all the services are allowed to grant age waivers.

Age Waiver Requests

Though you technically can join the military up to age 42, if you're 35 or over you'll need an age waiver if you've never been in the military before. Normally, military recruiters prepare and forward age waiver requests, with a yes-or-no recommendation for prospective recruits exceeding enlistment or commissioning age limits. Generally, each military service's personnel headquarters makes the final decision on all prospective recruit age waiver requests. Military age waiver requests are decided based on service needs and each prospective recruit's particular case.

Short-Staffed Career Fields

All military service branches manage staffing numbers within each of their career fields in addition to their overall authorized troop levels, or end strength. For example, at certain times the Marine Corps might need more communications specialists than they do tank mechanics. Your chances of joining the military at age 35 or older improve when you agree to work in a short-staffed career field of the military's choice. Also, military age waivers are frequently given to those possessing certain professional skills, such as physicians.

Joining the Military

If you're 35 or older and hoping to join the military, contact a recruiter representing the service branch you wish to enter. Your hoped-for military service branch's recruiters always have the latest information on enlistment and officer commissioning age limits. Military recruit training, or boot camp, and many officer initial entrance training programs can be physically demanding, especially if you're older. If you're 35 or over and approved to join the military it's wise to get into good physical shape before reporting for training.