Judges said the Finnair state loan guarantee was necessary in order to remedy the serious disturbance in the Finnish economy in view of the importance of the carrier for that economy.
Member states are negotiating final details of the so-called digital green certificate and the parliament is hastening a vote, expected to be held during its next plenary June 7-10.
"We expect this announcement will have a direct and immediate impact not only on our national vaccination plans, but also in our citizens' trust in vaccines against COVID-19," the letter said.
The EU is grappling with a slow vaccine rollout caused by supply problems and by repeated changes in the use of the AstraZeneca shot, which have increased vaccine hesitancy.
Earlier this month, Iranian supreme leader Ayatollah Ali Khamenei said his country may return to full compliance of the JCPOA if Tehran deems Washington has honoured its commitments.
The overall figure was revised down dramatically after the Anglo-Swedish pharma giant AstraZeneca slashed the number it was providing from a contracted 120 million doses.
Germany on Tuesday became the latest in a series of countries to advise against using the AstraZeneca jab for younger people after rare reports of clotting.
The 27 European Union member states highlighted "the need for further work to study the origins of the virus and its route of introduction to the human population".
Credit insurer Euler Hermes estimates that the EU is now seven weeks adrift of its target to have 70 percent of the population vaccinated by the end of the summer, compared with five weeks in February.
The Europeans are angry that UK-based pharma giant AstraZeneca has failed to meet its vaccine delivery promises to the EU while ensuring smoother supplies to former member Britain.