When I inquired of my state board regarding this matter, I was told that to petition the 18-month window, I needed to (1) pass all four parts of the exam and THEN (2) apply for my license. In doing so, I would have been required to attach proper documentation as to why I was not able to pass within 18-months (such as letters from physician(s), copies of military call up papers, copies of death notices, etc.). Granted, I did not have to petition the 18-month window because I successfully passed both of my exams on my next attempts, I was told that generally the board has accepted – medical conditions experienced by the applicant or a close family member; the applicant's being called into active military duty; a death in the applicant's family; hardware or software failure at the testing site; unexpected closure of the applicant's testing site due to inclement weather, etc.
FAR - 76 (Lost credit), 76
AUD - 80
BEC - 76
REG - 75
Truly I tell you, if you have faith as small as a mustard seed, you can say to this mountain, "Move from here to there," and it will move. Nothing will be impossible for you.