Enlightenment about an Aircraft

Hello ,

I have been observing some white smoke trails in the air.
I first tough maybe they were meteorites,since where the trails started seemed to come from outer space but i could not confirm since the objects causing the trails appeared before i could even look at them.
And they were far gone after.
But just before January new year i actually saw one of these objects coming out of space and moving at high altitude and at a high speed and making a little noise like an aircraft engine.
The smoke trail remains there for about 15 minutes and scatters radially,thats its like it spreads about the radius of the smoke trail.
When it passed above me,i was surprised to discover it was actually an aircraft,white in colour and moving at a very high speed.
Then it disapeared once again into space.
I do believe in UFOs but i think this is a human aircraft test.
The problem is there is no test base near me.
I live in Cameroon,
in the African Continent and that is really weird.
Some time later i observed this time a military aircraft that was like looking for something specific.For sure its not a cameroonian aircraft since it was blueish and looked like an AWACS with the circular radar at the top.

Could someone tell me something about those aircrafts.
Thanks.

There are many stories about some UFOs being able to cloak with fog as well as some UFOs being able to move in and out of the visual spectrum. Sounds like you had a good experience with something.