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: 
Landing gears are generally retracted to decrease drag in flight . As the speed of 
an aircraft increases, so does parasite drag. Mechanisms to retract and stow the landing gear to eliminate parasite drag add weight to the aircraft. 

Private Jets generally use Tricycle-type landing gear with dual main wheels . One of the main advantages of using the Tricycle-type landing gear is that it prevents ground-looping of the aircraft. Since the aircraft center of gravity is forward of the main gear, forces acting on the center of gravity tend to keep the aircraft moving forward rather than looping, such as with a tail wheel-type landing gear.

It is not necessary to retract the landing gear . Infact there are Landing gears that are Fixed as can be seen in many small, single engine , light aircrafts . 

On certain occasions Private jets as well as large aircrafts like the Boeing 777 extend their landing gear during flight **to cool the Brakes** because :

1. *The brakes may have been heated by the previous landing and not had time to cool while the airplane was at the gate*.
2. *During taxi out, they were further heated by necessary brake applications*.
3. *After takeoff, the landing gear retracted into the wheel well where there is limited cooling air*.
Sure it's a private ***jet***? Plenty of single-engine piston powered aircraft have fixed landing gear.

Most jets cruise at high altitudes, so if you can a) see the aircraft, b) identify it as non-commercial, c) notice the landing gear is down, and d) claim that it's not near an airfield then it's more likely that it is a 4-6 seat piston single with fixed gear. Cessna, Piper, Beechcraft have made thousands.

Addendum to edited question:
You say there are no airports *near by*. Possible there's one a little further away? Planes typically raise the gear as soon as they are off the runway, but they lower it 30km out. And that's 30km flying distance, not driving diatance.