The new flights from Birmingham Airport will operate each Tuesday and Saturday, in addition to the current Monday and Thursday services.
Icelandair first launched the Birmingham to Reykjavik service in February, increasing its London Gatwick service at the same time.
Paul Kehoe, chief executive at Birmingham Airport, said: "Icelandair launched their Birmingham to Reykjavik service in February and it has gone from strength to strength in that short time.
"It’s great to see the airline respond to the passenger demand for this service by increasing the number of flights. Passengers are set to enjoy greater choice and flexibility, whether they want to stay in Reykjavik and explore all that it has to offer, or travel onwards to the USA and Canada, using Icelandair’s strong network of connecting flights."
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