A procedure for the temporary use of special event call signs has also been established by the Federal Communications Commission. The FCC has set aside all one-by-one call signs to be used ...to meet the needs of amateur operators for temporary operation of their stations during events that are of special significance to the amateur service community.
The special event call sign is temporarily substituted for the call sign shown on the license of the person making the request while the station is transmitting in conjunction with the special operation.
A one-by-one call sign consists of a single prefix letter (K, N or W), the region number (0 to 9) and a single suffix letter (A to Z with the exception of the letter X). An example of a one-by-one call sign would be W1A. There are 750 such call signs - none of which are currently permanently assigned.
Unlike the vanity call sign system, there is no cost to obtain a temporary special event one-by-one call sign. The request must indicate the nature of the event and include the licensee's name, address, and primary call sign. It is not necessary that the geographical numeral in the call sign coincide with the licensee's mailing address or the location in which the operation is planned.
The first assignable call sign on the list is granted. The special event vanity call sign may be used for a period not to exceed that of the special event, or for 15 days whichever is less. The FCC has an online bulletin entitled The Special Event Call Sign System. You may learn more and reserve a One-by-One Special Event Call Sign