An F-35 Lightning II flies overhead for the first time at Eglin Air Force Base in Florida. (Senior Airman Julianne Showalter/U.S. Air Force via Associated Press)

An airman stationed at Creech Air Force Base in Indian Springs, Nev., was denied reenlistment because he omitted the part of a required oath that states “so help me God,” according to a letter from the American Humanist Association. The letter was sent on Tuesday to the Air Force’s Office of the Inspector General on behalf of an unnamed airman.

The AHA said it is prepared to sue for what the organization says is a violation of the Establishment Clause in the U.S. Constitution, unless the Air Force permits its members to enlist without the religious portion of the oath. The letter says that the airman “was told that his options were to say, ‘so help me God’ or to leave the Air Force.”

It goes on:

“Further, he was told that he must sign the religious oath portion of the enlistment form without adjustment … this letter demands that you immediately allow [omitted] to reenlist using a secular affirmation and that the Air Force accept his written enlistment form in a way that reflects his secular affirmation (i.e. by line-out and initial of the ‘oath’ and ‘So Help Me God’ portions of DD Form 4.”

The Air Force has not confirmed several details of the incident. In a Friday afternoon statement to The Post, U.S. Air Force Public Affairs Officer Chris Hoyler said that “the Airman’s term of service expires in November 2014.  He has until this time to complete the Department of Defense Form 4 in compliance with the Title 10 U.S.C. §502.”

Inquiries into the oath uncovered a change to Air Force rules last year that previously went unnoticed, as the Air Force Times noted. Until October 2013, Air Force Instruction 36-2606 (which governs the enlistment oath) included a short note: “Airmen may omit the words ‘so help me God,’ if desired for personal reasons.” That was removed in an amendment to the rule, effective Oct. 30, 2013, according to the Air Force Times.

Speaking to the Huffington Post, U.S. Air Force Public Affairs Officer Chris Hoyler said that the change now makes “reciting ‘So help me God’ in the reenlistment and commissioning oaths…a statutory requirement.”

According to the Air Force’s statement to the independent Air Force Times, Congress would have to change the statute mandating that part of the oath in order for the Air Force to make it optional again.

Now that it has the attention of the AHA and the Military Association of Atheists and Freethinkers, the policy change seems bound to become another source of disagreement over the role of religion in the U.S. military.

The Air Force, in particular, has faced intense scrutiny for what some believe is a preferred status for Christians in the service and at the Air Force Academy in Colorado Springs, Colo.

Critics, including Michael Weinstein’s Military Religious Freedom Foundation, have in the past lobbied for changes to the way the Air Force references God and the Bible. For example, in 2011, the group helped to successfully eliminate an Air Force nuclear training program that taught ethics using Bible passages and religious figures for reference.

And in the same month that the Air Force’s enlistment oath rules changed to make the “so help me God” portion mandatory, the Air Force Academy announced that it would allow its cadets to opt out of the very same phrase in the honor code.

Those changes, however, have angered some conservatives and evangelicals in and out of the Air Force, who believe that many accommodations designed to protect religious minorities in the service violate the Christian majority’s right to religious freedom.

A 2012 Air Force Times survey about perceptions of religious freedom in the service found both atheists and Christians in the Air Force complaining of a need to “walk on eggshells” about the issue.

As McClatchy reported, conservative groups and Republicans in Congress heavily criticized the Air Force for a rule change that prohibited commanding officers from “the actual or apparent use of their positions to promote their religious convictions to their subordinates.”

While conservatives argued that the regulation prevented those officers from expressing their religious views, the regulation’s supporters believe that it’s necessary, given the hierarchical nature of military culture. As of May, that rule was under review by the Air Force.

[this post has been updated]