Death Watch - S3-E19
Continuity mistake: At Harm's apartment, when talking to Mac about Cmdr. Krennick's advances towards him, he tells Mac that he wouldn't get involved with a superior officer, anymore than she would. However, it had already been established earlier this season in "For The Good of the Service" that Mac had a romantic relation with her Commanding Officer, Lt. Colonel Farrow.
Chosen answer: When landing on an aircraft carrier, a pilot "calls the ball" by confirming to the landing signal officer (LSO) that they have the carrier, and more specifically its landing guidance systems in sight. Carriers use a Fresnel lens system which is a light only visible at a certain angle, so if a pilot sees the "ball" they are at the correct altitude and glide slope for landing.
Sierra1 ★