India, May 14 -- Clogged lavatories have disrupted two of Air India's international flights in the span of two months, drawing attention to how aircraft toilets operate. All but one of the toilets on a Boeing 777 (B777) from Chicago to Delhi became unusable in March, forcing the aircraft to return, and at least five toilets clogged on a B777 from Toronto to Delhi this month, forcing a diversion to Frankfurt.

A B777 typically has 12 toilets, but why should so many clog simultaneously? The key factor is the location of the objects causing the blockage - often polythene bags or pieces of cloth - which can affect all toilets whose waste lines pass through that area. But, regardless of whether one or multiple toilets are affected, such blocka...