My silver dishes, tea set, etc. that previously needed polishing once or twice a year are now turning black in just a few weeks. This area has low-flying planes. Could they be releasing sulphur which causes the blackening of silver?
There are 3 main culprits for the silver tarnishing reaction: hydrogen sulfide, water, and oxygen. Please note that sulfur dioxide doesn't (directly) contribute to this. Airplane exhausts are principally CO2, H2O, and NOx with small amounts of ozone, sulfur dioxide, and particulates. Note: no H2S (hydrogen sulfide). Increased humidity is one obvious reason why you might see an increase in the rate of tarnishing - have you changed the heating/air conditioning that your silver is exposed to? Is the weather wetter now than in the past? It's also been established that NOx accelerates tarnishing - and anything that burns (in air, which is 78% N2 and 21% O2 and about 1% H2O) makes NOx. (NOx is shorthand for a family of nitrogen oxygen compounds). It gets worse: the more you polish silver the faster it tarnishes. So, you'd expect the longer you own the silver that you'd find an increasing need to polish it if you wanted to maintain its silvery appearance (and didn't use it much). There are other environmental sources of H2S: volcanoes, gas wells (frakking has increased dramatically in the last 2 decades), chemical plants, sewers, water treatment pools, landfills. So, while it's possible that increased emissions from near-by internal combustion engines (cars and planes and boats) could be making the problem worse, I'd not expect aircraft emissions to have much of an effect. I've read (but have no personal experience with) anti-tarnish bags, cloths and strips do wonders. Also, you should consider a well sealed cabinet perhaps with a desiccant (remember humidity accelerates tarnishing) if you display your silver. The experts use activated carbon and zinc oxide in their cabinets to absorb the H2S, but that seems excessive for home use. I'd try the 3M strips and as small an air volume as possible. I'd also be willing to try large desiccant packs but have some doubts that they'd work for long enough to be worth while (unless you kept the cabinet or bags really well sealed and almost never opened it). Just my 2 cents, HTH. I should also mention that kitchens (and compost) can be a significant source of H2S.