Norwegian Air has earned a name for its low-cost deals, such as £99 one-way flights from Edinburgh and Dublin to New York.
However, it posted a net loss in 2017 and had to raise fresh funds earlier this year to cope with its rapid expansion and higher fuel costs.
Nevertheless, its move into discount intercontinental flights has shaken up the market and forced bigger rivals such as IAG and Air France to take measures to win back customers.
IAG has already put a toe in the budget long-haul market with Level from Barcelona, while adding European airport slots from failed UK airline Monarch.
'Poaching'
IAG chief executive Willie Walsh has long been interested in low-cost long-haul concept long before it set up Level, said Liberum analyst Gerald Khoo.
"This may be an attempt to accelerate its development, while also adding to the scale and reach of [IAG-owned] Vueling in the intra-European market."
This week, BA began selling "Basic" tickets from London to destinations including Boston, Delhi, Dubai, Hong Kong and Singapore.
Fares start from £143, but passengers must pay £60 to check a bag and £20 for seat selection.
Simon Calder, travel editor of the Independent, told the BBC: "The main purpose of this initial move is to get more competitive with Norwegian, which is building an extensive network from Gatwick and poaching passengers from British Airways. Most of the first 10 destinations are on the Norwegian network."