Littler, who turns 17 on 21 January, was serenaded by the Alexandra Palace crowd as the pair warmed up, with “there’s only one Luke Littler” and “walking in a Littler wonderland” ringing round the famous amphitheatre.
Many pundits predicted that Littler would outscore 2018 champion Cross, 33, and that ended up being the case, despite some initial scrappy and nervous darts.
He finished with a three-dart average of 106.05 compared to Cross’ 102.77.
It is the fourth match of the tournament that Littler has averaged more than 100. No other player has done that with already eliminated Chris Dobey next on three occasions.
Littler started the tournament ranked 164th in the world and had a provisional ranking of 50 heading into the semi-finals. He could rise as high as ninth and win £500,000 if he is successful in Wednesday’s final.
He had only played four senior matches at PDC premier events before making his debut on 20 December and now has the opportunity to be the youngest winner of the tournament, surpassing Michael van Gerwen, who was 24 years and nine months old when he won his first title in 2014.
Littler lost the opening set for the first time in the tournament before he recovered to take a 3-1 lead, including taking out 142 in the third set.
Cross won the next set, breaking Littler’s throw with a 138, before he struggled to keep up with his opponent’s high-scoring game as the 16-year-old won three sets in a row to seal the victory.
Littler threw 16 maximums, compared to Cross’ 10, but it was the checkout accuracy that really cost the former champion.
At one stage Littler’s checkout percentage was 64.7 and Cross’ 34.8. That closed to 46.8 and 41.7 by the end but the Warrington teenager had opened up too much of a gap at that point.
“I just wanted to win my first-round game,” Littler told Sky Sports. “I heard he [Christian Kist] was struggling with an injury but I blocked it out. I knew I was spending more time in London so then my next target was to spend Christmas with the family and then come back and I did and here I am in the final.
“I’ve just settled on that stage. It takes me a few legs to settle but then I’m good to go.
“There’s no more development tour for me now! I’m happy to be in the top 32 and I can go even higher.”