Archer Aviation is on the cusp of big things, but it still has to hit a few milestones before it has air taxis flying in the U.S. market.Archer Aviation's (ACHR 5.14%) stock hasn't had a particularly good year, with the shares trading near their 52-week lows. But if the second-quarter earnings release is any indication, it is achieving some important progress as it looks to develop an air taxi and air taxi services. Here's a look at the buy, sell, and hold thinking on Archer Aviation.Buy Archer AviationWhen ...