Two things: closed-door suites and lie-flat seats. Credit: Courtesy of Qatar Airways Qatar Airways A350 Qsuite offers full privacy with 52-inch-high walls and sliding doors in business class. Singapore Airlines’ A350-900ULR pods provide a dedicated "bed mode" with exceptional comfort on the longest flight. JetBlue's A321LR Mint Studio features spacious closed-door pods and invites guest interaction in-flight. Business-class air travel has come a long way over a short period. It was initially conceived as an intermediate-level product somewhere in between economy and first-class. You needn’t be too seasoned of a flier to remember when the business-class cabin was characterized by dense stacks of Lay-Z-Boy-like recliners offering little else by way of meaningful amenities. A lukewarm towel, perhaps?  British Airways elevated things to new heights in March 2000 with the introduction of the first-ever convertible lie-flat seat. Business-class travelers could now enjoy a bed in the sky.…