|Per the FCC, the following call signs are NOT available for assignment under the Vanity call sign program:
(1) KA2AA through KA9ZZ, KC4AAA through KC4AAF, KC4USA through KC4USZ, KG4AA through KG4ZZ, KC6AA through KC6ZZ, KL9KAAthrough KL9KHZ, and KX6AA through KX6ZZ;
(2) Any call sign having the letters SOS or QRA through QUZ as the suffix;
(3) Any call sign having the letters AM-AZ as the prefix. These prefixes are assigned to other countries by the ITU.;
(4) Any 2-by-3 format call sign having the letter X as the first letter of the suffix. These are assigned to experimental (non-Amateur) stations;
(5) Any 2-by-3 format call sign having the letters AF, KF, NF, or WF as the prefix and the letters EMA as the suffix. These have been allocated to (U.S Government) Federal Emergency Management Agency (FEMA) stations;
(6) Any 2-by-3 format call sign having the letters AA-AL or NA-NZ as the prefix ;Any 2-by-3 format call sign having the letters WC, WK, WM, WR, or WT as the prefix (Group X call signs).
(7) Any 2-by-1, 2-by-2 or 2-by-3 format call sign having the letters AH, AL, KH, KL, KP, NH, NL, NP, WH, WL or WP as the prefix unless your mailing address is outside of the 48 contiguous U.S. states. These prefixes are available ONLY to radioamateurs with non-contiguous U.S. mailing addresses in the state of Alaska and Hawaii and certain U.S. possessions. (Such as Guam, American Samoa, U.S. Virgin Islands, Puerto Rico and other small island possessions.)
(8) Any 1-by-1 format call sign. These are reserved by the Special Event Call Sign System. (For example: K1A.) Note: 1x1 call signs with a "X" suffix letter is not assignable.
(9) Station call signs that have been inactive for less than two years. As a general rule (exception No. 1, No. 2 and No. 3) a call sign may not be reassigned under the Vanity call sign system unless it has been inactive for a minimum of two years following expiration, revocation, cancellation, relinquishment or death of the applicant.