<p>From ww.usna.edu:</p>
<p>The USNA uses a selection process known as “rolling admissions.” As soon as all of your candidate packet forms are received, the Admissions Boards will determine your scholastic “whole person” qualification. If your record of achievement is truly outstanding, you could receive an early offer called a Letter of Assurance. This indicates our intent to extend an Offer of Appointment, provided all your remaining requirements (nomination, CFA, Blue and Gold Officer interview and medical) are successfully completed. A Letter of Assurance could be received as early as September of your senior year. Of course, final admission will depend on continued success and good standing in your high school as well as continuing to maintain your qualifications for the Naval Academy.</p>
<p>If you are found scholastically qualified but do not receive a Letter of Assurance, you will be competing for an Offer of Appointment from within your nominating sources. Approximately 2,000 candidates are found fully qualified (scholastic, medical, CFA, and have obtained a nomination) each year. Of that number, about 1,500 will receive appointments and approximately 1,200 become midshipmen. Most candidates will be notified of their final status by April 15. </p>
<p>Bottom line as I read it is that a LOA is not a guarantee of an appointment, but it is close.</p>