The pilot of the plane which crashed into the English Channel with Emiliano Sala on board, was not qualified to fly at night, according to BBC Wales.
David Ibbotson is thought to have been colour-blind, and his licence restricted him to flying in daytime hours only.
Footballer Sala, 28, died when the plane carrying him from Nantes to Cardiff crashed late on 21 January.
The UK Civil Aviation Authority (CAA) said it could not comment.
The Air Accidents Investigation Branch (AAIB) said licensing "continues to be a focus" of its investigations.
Regulatory authorities have confirmed that Mr Ibbotson, from Crowle, North Lincolnshire, did not hold a "night rating" on his UK private pilot's licence, the BBC understands.
His UK licence was mirrored by a US pilot's licence - enabling him to fly the US-registered Piper Malibu in Europe.
The public record of his Federal Aviation Administration (FAA) licence states Mr Ibbotson "must have available glasses for near vision" and that "all limitations and restrictions on the United Kingdom pilot licence apply".
There is no publicly available record of UK pilot licences, which are held by the CAA.
But sources have told BBC Wales that Mr Ibbotson's licence restricted him to "flights by day only".
An aviation source told BBC Wales that the ability to be able to differentiate between green and red lights is "key" to flying in the dark.
"Anything that's on the UK licence applies to the US licence as well, so he couldn't do anything more than the UK licence allows.
"Flying outside the restrictions of your licence is illegal and that's likely to affect the insurance cover for the flight."
European aviation rules define night as "the time from half an hour after sunset until half an hour before sunrise".
Flight plans seen by BBC Wales indicate the flight scheduled to take Argentine player Sala for his first training session with Cardiff City had been due to leave Nantes airport at 09:00 local time on 21 January.
But the flight was postponed until 19:00, at the request of Sala, to allow him to spend the day saying goodbye to his Nantes teammates.
By the time Mr Ibbotson taxied a Piper Malibu plane on to the runway ready for take-off shortly after 19:00, it would have been around an hour and 10 minutes since sunset.
Speculation about the legality of the flight has so far centred around the question of whether it complied with restrictions concerning private pilots flying passengers in Europe in a US-registered aircraft.
As a private pilot, 59-year-old Mr Ibbotson was not allowed to carry passengers for remuneration or financial reward.
A preliminary report from the AIIB, released in February, stated he could only fly passengers on a cost-share basis.
As the aircraft was US-registered, pilot and passenger must have a "common purpose" for making the journey, and the pilot must dictate when a flight leaves.
The report adds that the flight "must not be made for the purpose of merely transporting the passenger".
In an interview in February, football agent Willie McKay, who commissioned the flight, told the BBC that he and his family paid for the flight.
He was not involved, he said, in selecting the plane or the pilot and it was not a cost-share arrangement.
The plane disappeared off radar north of Guernsey in the Channel Islands at 20:16.
Sala's body was recovered from the wreckage of the plane in early February but Mr Ibbotson's body has not been found.
The European Aviation Safety Agency (Easa) states that to obtain a night rating, a pilot must undergo five hours of theory and five hours of flight training.
In their preliminary report, the AAIB said that because Mr Ibbotson's pilot licence and log book had been lost in the crash, it had not yet been able to establish what ratings he held or how many hours he had flown recently - although it was known he had completed approximately 3,700 flying hours.
Investigators would normally look to establish how many hours a pilot had flown in the last 28 and 90 days before a crash.
The AAIB is expected to publish its full report into the tragedy early in 2020.
saleem26
1
burn in hell? WTF!!!!!
right he deserves to be in heaven
Anyamichael
1
what do you want to do now?the man is dead and gone .stop this nonsense
cupdekmst
2
as a united funny rip sara
cupdekmst
4
ya may his soul rest in enteral peace young sarah
Jackiexyz
0
burn in hell? WTF!!!!!
so what? no one lives peacefully in hell, people like Sala who are destined to go to hell burn forever
Wawakruyz
2
RIP
Richieefundz
0
what's the problem of the as authorities?!Sala is fucking dead, just let him burn in hell, why are they investigating more about the crash!!
burn in hell? WTF!!!!!
Hekabmt
2
R. I. P.
MadridCity810
0
what's the problem of the as authorities?!Sala is fucking dead, just let him burn in hell, why are they investigating more about the crash!!
You have no way of understanding the greif that his family, fans and friends are and were going through. You are a heartless person at its worst. Im dissapointed with this generation.
luzabkrstz
1
may God continue to guide the family you are left
Piailrtuy
0
what's the problem of the as authorities?!Sala is fucking dead, just let him burn in hell, why are they investigating more about the crash!!
senseless
connectrawl
0
Maybe Nantes fans killed him because they were jealous he was making money
Watch what you say bro! that's a serious allegation. let's try to comment within the context.
connectrawl
3
Rest In Peace Sala
widabdmnsy
3
Investigations are good to prevent recurrence of such unfortunate incidences. RIP Sala, watch on us as we pray for you and your family.
⚽CR7FOREVER⚽
0
what's the problem of the as authorities?!Sala is fucking dead, just let him burn in hell, why are they investigating more about the crash!!
heartless motherfucker barca fan
jipbdilnpt
9
AF we should not talk about them anymore, we should respect them and let them rest in peace.
Wuedeilnr
0
Cardif should return the transfer money to nantes😂
rihcnosy
0
rip
Zuudntz
0
what's the problem of the as authorities?!Sala is fucking dead, just let him burn in hell, why are they investigating more about the crash!!
So mean
Reddevilsalways
2
Please let them RIP...
Dodcikotyz
3
....but where is the pilot?
SirLammy
0
I am surprised people are saying stop the story and investigation, they are dead now forgetting that investigation is the key to stopping future occurrance of this kind of tragedy.. Is only in nigeria that they dont investigate incidence and they leave it to God to judge.
even in Nigeria they investigate. know your fact. stop painting is black to the world dude.
SirLammy
0
Maybe Nantes fans killed him because they were jealous he was making money
how's that even possible?
Neeoru
0
what's the problem of the as authorities?!Sala is fucking dead, just let him burn in hell, why are they investigating more about the crash!!
Heartless.
Jackiexyz
2
what's the problem of the as authorities?!Sala is fucking dead, just let him burn in hell, why are they investigating more about the crash!!
BawSkee
0
The pilot looks like shane machman from wwe😂😂
No he doest not even a little wtf.
HalaHussein007
1
After all these infos, it seems like Sala's death was planified from the start
yosabdimpy
0
Maybe Nantes fans killed him because they were jealous he was making money
That was what his ex said so who knows
gentlesoulnw
1
So is it safe to say Sala chose the timing of his death... 9 o'clock to 7 o'clock. Continue to RIP
Zucabkotuy
3
Maybe Nantes fans killed him because they were jealous he was making money
scofeeld
6
we have lost a good player let's forget about pointing fingers and just say R.I.p because to points fingers will not bring them back
Dortmundftw
3
The pilot looks like shane machman from wwe😂😂
Tonbcilnpy
1
SAFETY reasons the truth must be disclosed to all irresponsible people must be taken to.task ....how bad it will take to prevent the recurrence of this crash is of utmost importance.
Vibilpstu
1
Rest in peace salla gone but not forgotten.but Media's should stop creating another useless behavior hear they r all gone.
obaidblsh
0
This is all management fault
SeriesA
1
WTF!! Go and kill him again..lol
Sipbcdemos
3
I am surprised people are saying stop the story and investigation, they are dead now forgetting that investigation is the key to stopping future occurrance of this kind of tragedy.. Is only in nigeria that they dont investigate incidence and they leave it to God to judge.
Elsa98
7
The pilot is the one to blame.😔 I hope that sala rests in peace.🕊️🙏🏻
duhbnuz
1
they are all gone and nothing is there to do and bring them back so let's believe in God and stop all this bullshit news
VanishPrasad
2
Gibe but not forgotten. Rest in peace Salah. I never watched you play, I never saw your live goals and performance but everyone knows that you're a kind hearted person. We all miss you
JustGoWithIt
2
Once A Footballer Always A Footballer
Gone Too Soon But Will Never Be Forgotten
#SIP Sala 🙌
Spartacus_Aye419
2
Same old Story !! Can the Press just allow these Guys Rest In Peace ?? Cos these same old stories won't bring them Back to Life, the more we see this irrelevant stories, the more his beloved ones would be remembering him and feeling Bad. Anyways R.I.P to them Both
Edoo87
1
both of them is dead now , R.I.P