This includes BA flights between Heathrow and New York's JFK airport, Italy, France, Austria, Belgium, Germany, Ireland and Switzerland.
The airline has also cancelled flights between Gatwick and Italy, France and Albania, as well as London City flights to and from Germany and Italy.
A British Airways spokesperson said: "To match reduced demand due to the continuing coronavirus issue, we are merging a number of flights between March 16 and March 28.
"We will be contacting customers on cancelled flights so we can discuss their travel options, including re-booking onto other carriers where possible, full refunds or booking with BA for a later date of travel.
"Customers can also find the latest information and options on BA.com."
Meanwhile Ryanair said it is reducing frequencies on some routes by up to 25%, which will particularly affect its flights to and from Italy.
The reduced schedule will operate from March 17 until April 8 following a “significant drop in bookings” over the period, according to the Dublin-based carrier.
As well as reducing flights, Ryanair said it is taking a series of measures in response to the coronavirus outbreak.
These include “rolling schedule cuts”, allocating leave or paid leave to pilots and cabin crew, working with suppliers to cut costs and freezing recruitment, promotion and pay across its network.
The moves by BA and Ryanair follow earlier flight cancellations by easyJet.