After five years at the helm of the drinks-and-snack giant, Nooyi is testing the patience of company directors who are fretting over the lack of an heir apparent amid a series of marketing missteps and a stock that is flat as day-old soda.

Sources close to the board said some members have expressed frustration that there is no succession plan and that the only potential CEO replacement, Eric Foss, who headed up the bottling operations, is leaving next month.