[MrB]

Oops, not 250 years, 250 FEET of ice.

Now, what is the assumption on how many feet/year that ice layers form?

If it’s inches, those planes traveled back in time THOUSANDS of years.

I bet the “ape men” were scared shtless.

[tacticalogic]

Now, what is the assumption on how many feet/year that ice layers form?

There don't make assumptions about the number of feet per year. Seasonal differences produce differences in the composition of the ice. Age is determined by counting the individual seasonal layers. It is not based on assumptions about how many feet of ice are deposited per year.

[tacticalogic]

On what basis should we assume that the ice covering that plane was not deposited since it landed?

You're proposing that we should assume there is something horribly wrong with what appears to be a reasonable and intuitive assumption about the ice covering that plane, for no apparent reason.

[stormer]

“If it’s inches, those planes traveled back in time THOUSANDS of years.”

Hmmm... I've lived in a place that received around 500 inches of snow per year. If that snow did not melt (it did where I lived, thankfully) and if compressed to 10 percent of its original depth to account for lost interstitial volume, we arrive at an ice depth of around 4 feet. At four feet of accumulation per year for the intervening 60 or so years, the resulting figure is quite close to the 250 feet you've mentioned. I guess I've missed your point.