Red Bull published a tantalising teaser on Twitter of their RB19 lapping at Silverstone while Alfa Romeo said their C43 completed a successful debut at Barcelona's Circuit de Catalunya.
Red Bull held a livery launch in New York last week with double world champion Max Verstappen (25) and Mexican Sergio Perez (33) while Alfa showed off their new look in Switzerland last Tuesday.
Alfa will also be doing a second promotional filming day on Saturday with race drivers Valtteri Bottas (33) and Guanyu Zhou (23) and reserve Theo Pourchaire (19).
"The debut of our C43 is a pivotal moment in our season: it marks the start of our on-track campaign and really drives home how close the season is," said Alfa technical director Jan Monchaux.
"Today was important to ensure everything is in place, not just with the car but also with the wider team, ahead of what is going to be a crucial start of the championship."
Testing is in Bahrain from February 23-25 with the season opening race at the same track on March 5.
