For distances >600km, flying is usually 4x-10x faster at a similar price. At least in and around Germany. I assume in the US trains compare way worse, also because the distances are way larger.

Examples: “Normal” example: Stuttgart (Germany) -> Amsterdam (Netherlands) Train: 11h 10min - 241€ Plane: 1h 20min - 225€

Best case scenario for train in Germany at around that distance (because there’s a direct connection): München -> Berlin Train: 3h 54min - 167€ Plane: 1h 5min - 226€

Then why not use 1? It’s closer to pi than 10 and even easier to calculate with.