Nearly 250 flights into Ireland have had at least one confirmed case of Covid-19 since January 1, but up to 80% of close contacts on some planes have never been traced.In more recent weeks, over 50 of those flights have included cases of the so-called ‘variants of concern’, according to correspondence from a concerned tracing employee shared with Social Democrats TD Catherine Murphy.The tracer supplied a number of examples of problematic flights which have arrived in Ireland over the past four months. 
One flight from western Europe in early April saw two positive cases that had originated their journeys in India, currently the source of a troubling new variant.
Of 23 close contacts, five, or 21%, were deemed uncontactable, while two others who were contacted tested positive, with the tracer suggesting it seems clear they picked up the virus on the flight.
Another example involved a flight from the US with a positive case of a variant of concern  on such long-haul flights, all passengers are considered to be close contacts, rather than just those passengers in the adjoining two rows.
Of that flights 43 passengers, a fifth was never contacted, while it took seven days for the flight manifest to reach the tracing system. More than 40% of the flight passengers never availed of a HSE PCR test.
Tracing of flights is done using flight manifests, provided to the HSE by the airlines.
Concern over flight manifest quality
However, the quality of the manifests has been a source of concern, with frequently incomplete or erroneous data included, while the States stockpile of passenger locator forms is rarely accessed, despite being available to tracers from last December.
Flight manifests are typically not delivered to contact tracers until between seven and 10 days after the flight has landed in Ireland.
So the true rate of inflight transmission will remain a mystery, wrote the contact tracer. And the cases we miss will show up as increased community transmission.
The tracer described the US flight and the flight with confirmed cases originating in India as being the ones Im losing sleep over.
I cant understand why we cant track these people down and continually rely on flight manifests, said the tracer.
Ms Murphy described the dossier as being a real source of concern.
There has to be confidence that tracing of flights is being done and done right,” said Ms Murphy. 
“Theres a real risk of importing new variants, which are more difficult to track down and which put the entire vaccination programme at risk.”  
The HSE did not respond to a detailed request for comment on the issues raised by the tracer involved.