Narrative:

Aircraft X was about 15 miles east of ZZZ at 9000 feet when I observed that I was no longer receiving the mode C altitude. I asked the pilot to say altitude and he responded for me to stand-by. About 2 minutes later the pilot turned about 30 degrees left of course and had still not gotten back to me on their altitude. I asked the pilot if everything was ok and he responded no and that he wanted to divert to ZZZ. I issued the pilot a heading towards ZZZ and asked for their current altitude. The pilot then responded that they were at 9000 and had lost an engine and some instruments and declaring an emergency. I gave the pilot a descent to 2000 and advised them of weather at ZZZ; asked what runway they would like and advised them of runway lengths. The pilot said he wanted runway xx. The tower was notified and I obtained a landing clearance for the pilot. The pilot was cleared for the visual approach and cleared to land by me. Aircraft X landed safely. I realized after aircraft X was on the ground that I never cleared them to ZZZ. From the time the pilot told me that there was a problem to the time the pilot landed was only about 3 minutes. I will make it a part of my mental checklist to amend the clearance in cases of emergencies.

Google
 

Original NASA ASRS Text

Title: Controller reports of an aircraft that loses an engine; declares an emergency; and then lands at a new destination. Controller was concerned because he didn't give the aircraft a clearance to the new destination.

Narrative: Aircraft X was about 15 miles east of ZZZ at 9000 feet when I observed that I was no longer receiving the Mode C altitude. I asked the pilot to say altitude and he responded for me to stand-by. About 2 minutes later the pilot turned about 30 degrees left of course and had still not gotten back to me on their altitude. I asked the pilot if everything was OK and he responded no and that he wanted to divert to ZZZ. I issued the pilot a heading towards ZZZ and asked for their current altitude. The pilot then responded that they were at 9000 and had lost an engine and some instruments and declaring an emergency. I gave the pilot a descent to 2000 and advised them of weather at ZZZ; asked what runway they would like and advised them of runway lengths. The pilot said he wanted runway XX. The tower was notified and I obtained a landing clearance for the pilot. The pilot was cleared for the visual approach and cleared to land by me. Aircraft X landed safely. I realized after Aircraft X was on the ground that I never cleared them to ZZZ. From the time the pilot told me that there was a problem to the time the pilot landed was only about 3 minutes. I will make it a part of my mental checklist to amend the clearance in cases of emergencies.

Data retrieved from NASA's ASRS site and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.