Question: Are there situations in which a pilot could/has to lower the landing gear during flight for reasons not directly connected to landing? (i.e., not part of the landing checklist)

Originally I thought I had seen some around the location indicated by the pin on the map below (17° 25' 30.093" N, 78° 32' 27.4734" E), in the evening time around 4:00 and the weather was clear.

[![Sighting location](https://i.stack.imgur.com/78nOO.jpg)](https://i.stack.imgur.com/78nOO.jpg)

Answer: 
That's **nowhere near midflight**. You are seeing aircrafts approaching [Begumpet Airport (VOHY)](http://ourairports.com/airports/VOHY/)'s runway 27. This airport has no airline service, but it is used for some general aviation including VIP flights and as military airbase.

The point directly north (about 3 km) from the coordinates you gave ([N17° 25' 30", E78° 32' 27"](https://www.google.com/maps/place/17%C2%B025'30.0%22N+78%C2%B032'27.0%22E/@17.4532706,78.5342887,13z/data=!4m2!3m1!1s0x0:0x0)) is about 6 km, or 3.2 nm, from threshold of VOHY runway 27. Given usual 3° glide slope the aircraft would be just about 1000 ft above runway elevation, which happens to be the latest point where landing checklist should be complete. Yes, that means gear down. It also means it will be touching down in about a minute and a half.
The reasons I can think of offhand for extending the gear for other than landing are:

* As has been mentioned in a previous answer, use of the landing gear as a speed brake. The Fokker F-27 had a speed brake switch on the front panel that when used lowered the main landing gear but left the nose gear retracted. At the two 747 carriers I worked for in the 1990s, we occasionally dropped the gear to get more drag for a steeper descent. As I remember the max gear extension/retraction speed was 270 knots, but once extended the max speed was 320 knots.
* To cool hot brakes or hot tires. This was the most common reason in my experience for extending the gear. The 747-100/200 was supposed to be taxied at no greater than 25 kts, which meant that braking was needed during taxi even with engines at idle. Tire flexing also produced significant heat. There was a recommendation not to taxi more than 30,000 feet as I remember because of these factors. If you were using, say, the reef runway at Honolulu, you exceeded that distance by the time you lifted off, and if you were above 800,000 lbs you were guaranteed serious heating.
* To pre-cool the brakes and tires if you had a short leg followed by a quick turn. The 747 was originally designed to stay in the air for awhile before landing. The story I most often heard was they designed for 5.5 hours of cooling in the wheel wells before the gear would be used.
* To burn extra fuel to get below landing weight. Rare, but it could happen if you were tankering fuel such to arrive at max landing weight and for whatever reason the leg burn was less than planned. Fuel burn increase with the landing gear down is quite dramatic. We were tankering fuel once from Yakota, Japan to Osan, Korea, and we couldn't get the landing gear up. Our choices were to dump fuel and return to Yakota or to proceed to Osan with the gear down. We chose the latter. We couldn't get above 25,000 and our fuel burn was twice normal. Confused the controllers; they kept wondering by we were so slow and so low. We kept having to explain.