The prototype was developed as a response to the phasing out of Federation-class dreadnoughts in favor of smaller and less costly Avenger-class heavy frigates as well as Starfleet Intelligence reports of increased production of the K't'inga-class (D7M) battlecruiser in the Klingon Empire. It was felt that a large, fast vessel was needed for the mass transport of personnel into a battle zone.
The prototype, USS Calgary, had a displacement of 275,000 tonnes. Standard crew complement was to be 646, including 425 surface action specialists. Armaments included 22 phasers in 11 banks, plus two photon torpedo bays. Embarked attack fighters would be Cirrus-class battlepods.
Log entries from the flight tests indicated "a nearly perfect shakedown cruise."
- The Star Fleet Data File, vol. 1 gave no date for the construction of the prototype, so it was assumed that construction could take place no later than ca. 2287, after transwarp propulsion proved to be impractical and Ingram-class vessels were refit to an Excelsior-class heavy cruiser standard.