Protestant - 2,652 (59%)
Catholic - 1,339 (30%)
No religious preference - 243
None - 114
Jewish - 37
Atheist - 30
Buddhist - 26
Muslim - 14
Hindu - 6
Orthodox - 5
Pagan - 2
Other - 26
Unknown - 35
Total - 4,529
Acknowledged Christians make up 88% of the Academy (numbers don't match due to ronding). About 9% chose one of three secular designations. About 2% have a non-Christian designation (assuming that "other" contains non-Christian religions - I suspect that some of those designations are basically secular or Christian), and about 1% have an unknown affiliation.
Academy students are less secular than the Air Force as a whole, where more than 18% are basically secular. Christianity Today notes:
A survey conducted by the Air Force in June  reveals that 0.6% of the 275,457 current enlistees describe themselves as "atheist" and that 17.8% have "no religious preference."
The survey, or at least this summary of it, fudges one of the deepest divides in the Academy and in the military generally. The divide between the Evangelical Protestants and the "liturgical" Protestants, data from a lawsuit in the late 1990s revealed that:
Of the 17 most influential jobs in the chaplain corps, eight are held by members of high-church Protestant sects, whose members include 15 percent of Navy personnel, and five by Catholics, who account for 24 percent of the Navy. The remaining four are held by low-church Protestants, who account for 41 percent — by far the largest religious group of Navy personnel, Pentagon statistics show. Most of the remaining 20 percent listed no religious affiliation.
If the Air Force is typical of the Navy (and it isn't entirely, and the Academy even less so, but there is no good reason to believe that the ratio of Evangelical to liturgical Protestant Christians is grossly off, although the relatively high Catholic percentage may indicate that AFA cadets are slightly more liturgical than other military groups), about 16% of cadets are liturgical Protestant Christians, and about 43% of cadets are evangelical non-liturgical Protestant Christians. The former may be a few percentage points low, the latter may be a few percentage points high.
It is safe to say that Evangelicals are a plurality, but not a majority religion in the United States military. Also, if the Academy is typical of the officer corps, it is safe to guess that the enlisted ranks are roughly twice as secular as the officer corps. This is a little surprising because officers are better educated than enlisted personnel on average, and most military officers in military academies receive their degrees in a engineering field (backgrond in the physical sciences is strongly associated with secular beliefs). Of course, the military culture has long been strongly religious.