500-1000, that's a big enough budget to get something rather good, but you say compact, is that shirt pocket compact or bridge camera compact.
Panasonic do a bridge, fz1000, supposedly fast to af, 25-400mm field of eqivilant lens with it f2.8-4. It gets good reviews, has a reasonabley big 1" sensor and a lot of bells and whistles. Might be worth a look
Good superzooms next to the above mentioned SX60 HS is the Nikon P610 an
the camera with biggest reach the Nikon P900 (83x zoom).
For a better IQ take a look at the Panasonic FZ1000. A bridge camera with a very fast AF and a good Leica zoomlens.
It has less reach. (16x), but it can be doubled with a function called iZoom.
The FZ1000 has a very good IQ and it's the most versatile camera I ever worked with.
Plane spotting is a rather specialized area for a camera. I assume you will want a fairly high degree of magnification to pull in specific airplanes.
One reason for looking at the superzoom cameras now available is the advantage of a camera/lens combination designed completely around each other. Most of the superzooms utilize a smaller sensor (the part which records the image data) than would a digital SLR. Combining the small sensor with the relatively long zoom power of the superzoom lens is beneficial as the two combine to a higher "relative" zoom power than you will find on any other camera type.
Most, though not all, of the superzooms also have the additional feature of
"digital zoom" which increases the amount of lens power by as much as 2 times the optical results. Therefore, a "relative focal length" of 1200mm becomes 2400mm. That's a phenomenal amount of zoom power from a very inexpensive package. The trade off is a slightly less sharp image as you are now using fewer of the camera's pixels to record the image. However, if you want the longest zoom with the highest magnification, this is the route to take.
Do be aware of the fact it is very difficult to hand hold a camera with such a long zoom. Due to the high magnification of the subject, any slight movement in the user's hands will translate into a very noticeable amount of image blur. Tripods are typically recommended for such use. Also, the trade off for zoom power is a lens which is not well suited to low light photography. Expect your best results with any of these cameras to be in full sunlight. As you increase the zoom of the lens, the lens will close down its aperture which reduces the amount of available light reaching the sensor. The more you zoom, the smaller the aperture and the less light can enter. So there are trade offs to these cameras.
Several of these cameras have older models which sell at steeply discounted prices. Buying, say, a refurbished Canon SX50 for example, can take the cost down to as little as $199. Zoom power increases each year so last year's model may be slightly less powerful in that respect but still a very capable camera.
I would like to thank everyone who posted for sharing your experience with me. Special thanks to soufiej for the great explanation i am given for the basics i should have known.
I assume i will have to choose either the Coolpix p900 or the FZ1000. (Or not?)
From your experience,which one would offer me the cleanest image at zooming,the fastest (auto)focus while recording a video and the best image at night recordings ?(Because i will be recording videos at afternoom to night hours as well - I apologize for not mentioning this before.)
While the P900 is not a bad camera and is fast for a superzoom, the FZ1000 has the best image, is the fastest and will give better results in low light.
This plane spotting video with the FZ1000, has night scenes from minute 23 on.
I've toyed around with buying a Nikon P900 for various things including planes.
The 2,000mm equivalent focal length can come in handy in good lighting conditions.
For a "compact" camera this (or one similar) would be what I would get.
But this depends upon the type of plane spotting you do.
Do you only go to airports and shot them landing and taking off?
such as ==> Air02-09
or small aircraft such as this => Air_20150621-04
Or do you like to determine landing patterns & flight patterns and catch them without their wheels down, and maybe making a turn ?
I've shot planes 9+ miles away and cropped the image to bring it in. The image was better on a Nikon d600 than a Nikon d7000 crop camera both using a Tamron 150-600 @ f/8 and Sigma 150-500 when I was doing testing.
I can see what's coming, or for instance select only FDX (Fedex) planes are they normally use DC-10/MD-11s which are neat to photograph.
But it all comes down to what type of plane spotting you plan on doing. If it's just at the airport then your options are quite numerous. The further out the plane is from your location then you need a larger zoom lens type camera.
Then you need to determine if you like to post process your images. For instance the P900 does not use RAW files, only JPEGs, thus that may be an issue for you.
My biggest issue lately is trying to get the international space station. Which is full of problems.