It has been three weeks since the war in Ukraine began. The fighting grinds on and there is no clear end in sight. But what are the potential paths forward in the coming days and weeks? On Wednesday, President Volodymyr Zelensky, in an address to Congress, proposed one such path, though it is an incredibly unlikely one: a no-fly zone over Ukraine. Elsewhere, Times reporting has suggested four other potential scenarios — a diplomatic end to the conflict; protracted monthslong fighting; China coming to Russia’s rescue; and President Vladimir V. Putin expanding the conflict beyond Ukraine’s borders. We explore these scenarios and consider which of them is most likely to occur. Guest: David E. Sanger, a White House and national security correspondent for The New York Times.