Upon a determination by the Secretary concerned that a member of the armed forces not covered by section 1201, 1202, or 1203 of this title is unfit to perform the duties of his office, grade, rank, or rating because of physical disability, the Secretary may retire the member with retired pay computed under section 1401 of this title, if the Secretary also determines that—

(1) based upon accepted medical principles, the disability is of a permanent nature and stable;

(2) the disability—

(A) was incurred before September 24, 1996, as the proximate result of—

(i) performing active duty or inactive-duty training;

(ii) traveling directly to or from the place at which such duty is performed; or

(iii) an injury, illness, or disease incurred or aggravated while remaining overnight, immediately before the commencement of inactive-duty training, or while remaining overnight between successive periods of inactive-duty training, at or in the vicinity of the site of the inactive-duty training, if the site of the inactive-duty training is outside reasonable commuting distance of the member’s residence;

(B) is a result of an injury, illness, or disease incurred or aggravated in line of duty after September 23, 1996—

(i) while performing active duty or inactive-duty training;

(ii) while traveling directly to or from the place at which such duty is performed; or

(iii) while remaining overnight, immediately before the commencement of inactive-duty training, or while remaining overnight between successive periods of inactive-duty training, at or in the vicinity of the site of the inactive-duty training; or

(C) is a result of an injury, illness, or disease incurred or aggravated in line of duty—

(i) while the member was serving on funeral honors duty under section 12503 of this title or section 115 of title 32;

(ii) while the member was traveling to or from the place at which the member was to so serve; or

(iii) while the member remained overnight at or in the vicinity of that place immediately before so serving, if the place is outside reasonable commuting distance from the member’s residence;

(3) the disability is not the result of the member’s intentional misconduct or willful neglect, and was not incurred during a period of unauthorized absence; and

(4) either—

(A) the member has at least 20 years of service computed under section 1208 of this title; or

(B) the disability is at least 30 percent under the standard schedule of rating disabilities in use by the Department of Veterans Affairs at the time of the determination.