The Final Countdown

In 1980, the USS Nimitz takes on a civilian observer Warren Lasky (Martin Sheen), on the orders of his reclusive employer, Mr. Tideman as it departs Pearl Harbor for training in the Pacific.
Once at sea, the USS Nimitz encounters a strange storm-like vortex, which disappears after the ship passes through it. Initially unsure of what has happened, and having lost radio contact with Pacific Fleet Command, Captain Matthew Yelland (Kirk Douglas) orders General Quarters and, fearing the possibility of a nuclear strike on Hawaii, launches an RF-8 Crusader reconnaissance aircraft, which returns with photographs of the intact 1941 U.S. Pacific battleship fleet at Pearl Harbor.[Note 1]
When a surface contact is spotted on the radar, Captain Yelland launches the ready alert, two Grumman F-14 Tomcat fighter jets, to intercept. The patrol eventually witness a civilian yacht being attacked and destroyed by two Japanese Mitsubishi A6M âZeroâ fighters, killing three of the crewmembers. The Nimitz rescues the yachtâs remaining survivors: the fictional US Senator Samuel Chapman (Charles Durning), his secretary Laurel Scott (Katharine Ross), her dog, Charlie and one of the Zero pilots. The Nimitzâs CAG (Commander, Air Group), Commander Owens (James Farentino), an amateur historian, recognizes Samuel Chapman as a politician who could have been Franklin D. Rooseveltâs running mate (and his potential successor) during his final re-election bid except for the fact that he disappeared shortly before the fateful attack on Pearl Harbor on December 7, 1941.
After a Grumman E-2 Hawkeye discovers the Japanese fleet poised to attack Pearl Harbor, the Nimitz crew eventually realize that they have been transported back in time to December 6, one day before the attack. Captain Yelland has to decide whether to destroy the Japanese fleet and alter the course of history, or to stand by and allow history to proceed as ânormalâ. The civilians and the Zero pilot are kept isolated, but while being questioned, the Japanese pilot grabs a weapon, kills his guards and holds the other survivors, the CAG, and Lasky as hostages, threatening to kill them unless he is given access to a radio so he can warn his commanding officers about the Nimitz, which is far more powerful than anything in the Japanese fleet. The Japanese pilot is eventually overcome and Laurel and Commander Owens become attracted to each other.
The senator demands for them to be taken to Pearl Harbor, but Captain Yelland sends the civilians with sufficient supplies via helicopter to an isolated Hawaiian island. The Nimitz launches a massive strike force against the incoming Japanese forces, but before they can reach the enemy armada, the time storm returns. After a futile attempt to outrun the storm, Yelland recalls the strike force, and the ship and the aircraft return to 1980 safely. Upon the Nimitzâs return to Pearl Harbor, the Pacific Fleet commander boards the ship to investigate. Meanwhile, Lasky and Laurelâs dog Charlie, upon leaving the ship, finally encounter âMr. Tidemanâ face-to-face, who is revealed to be a much older Commander Owens, along with his wife, Laurel.

Question: What does Captain Yelland do when a surface contact is spotted in the radar?
Answer: Launches the ready alert