Given a certain amount of practice, you should be able to get used to holding powerful binoculars steady enough to identify high flying aircraft without the need for image stabilisers. I bought a pair of 16x50 binoculars when I was 18 and they saw me for most of my life. 2-3 years ago I replaced them with 15x60s and, aged 62, can often read the registrations off airliners flying over our garden, up to around 10,000 ft. They also allow views of contrailing aircraft good enough to identify the airline with no trouble. Telescopes are excellent - we use our birdwatching telescopes at airports but they're not so easy for aircraft flying over as most tripods do not allow one to look vertically.
One good tip - always ensure that the object lens is at least 4 times the magnification for best light transmission. That is, go for 10x50 in preference to 20x50 and steer well clear of the amazing offers in weekend papers for the "most powerful binoculars" because they're usually not!!