I think the main thing to keep in mind here is that this claim was made by creationists who were hoping to invalidate something called the GISP2 ice core from Greenland, which shows 110,000 annual layers. Snow accumulates in the area of southern Greenland, where the planes were found, at a depth of 7 feet per year, while it accumulates one foot per year where the ice core was drilled. What's more, Kent Hovind is apparently not quite clear about the meaning of the "layers" answer he got.

This article by David Seely, The GISP2 Ice Core: Ultimate Proof that Noah's Flood Was Not Global, addresses all the points you raised and some additional ones. It explains several methods that are used for dating ice cores in Greenland and Antarctica (which presumably you understand is the one of the driest places on earth and therefore where annual layers are very thin). It also explains the details of the claims of a couple of creationists and the errors they have made. It's quite a comprehensive discussion of the subject and yes, it discusses the planes too and explains the likely reasons why they were buried so deeply.

Do you cross-check the things you read on AiG? When I research a subject I try to get as much information from different sources as I can. Believe it or not, Talk Origins is never the last word for me. I want to find out what other people are saying and what the general scientific consensus seems to be. I highly recommend it as a truth-finding methodology.