PARIS France (AFP) — Airbus said Tuesday that up to 628 of its popular A320 planes worldwide may need to be inspected for a metal plate “quality issue” that has come to light.

In a message to Agence France-Presse, the European aircraft manufacturer said the figure represented the “total number of potentially impacted aircraft” but “it doesn’t mean all these aircraft are necessarily impacted.”

It added that the number of planes earmarked for checks was “reducing day by day as inspections progress to identify those needing a specific action to be taken.”

On Monday, Airbus said it had detected the “supplier quality issue” but asserted the problem was “contained” and affected only “a limited number of A320 metal panels.”

Shares in Airbus plunged on the news that quality problems with fuselage panels had delayed delivery of some of A320 aircraft.

The reports of the new problem came after a separate incident in which Airbus last week said that some 6,000 of its A320 planes should not fly again until a software upgrade was made following an incident in the United States.

Produced since 1988, the A320 is the world’s best-selling aeroplane. Airbus sold 12,257 of the aircraft by the end of September compared with the sale of 12,254 Boeing 737s.