At least some wizards do know that Muggle flight methods exist.
Even Arthur Weasley, who doesn't know the proper name for "electricity" or "plumbers", knows what an airplane is, and that its function is to fly. Despite working in the Muggle Artefacts division of the Ministry, and being interested in Muggle technology, Arthur Weasley seems to be one of the wizards who understands Muggle technology the least. However, his greatest ambition is to find out how airplanes stay up, which shows that not only does he know the proper word for them, but he also has at least a basic understanding of what they do.
“Arthur, is that you?’
‘Yes,’ came Mr Weasley’s weary voice. ‘But I would say that even if I were a Death Eater, dear. Ask the question!’
‘Oh, honestly …’
‘All right, all right … what is your dearest ambition?’
‘To find out how aeroplanes stay up.” - Harry Potter and the Half-Blood Prince, Chapter 5 (An Excess of Phlegm)
Now, an airplane isn't a helicopter, and Draco isn't Arthur Weasley, but this does show that even wizards who might know little about Muggle technology can still know about their flight methods. It's true that Arthur loved and was fascinated by Muggles though Draco would look at Muggles with disdain, and therefore probably not be actively seeking knowledge of their technology. However, despite his efforts, Arthur was arguably less knowledgeable about Muggle technology than most wizards likely are. Writing an essay on why Muggles need electricity was an assignment for third-years taking Muggle Studies.
“Harry looked around at the cluttered table, at the long Arithmancy essay on which the ink was still glistening, at the even longer Muggle Studies essay (‘Explain why Muggles Need Electricity’) and at the Rune translation Hermione was now poring over.” - Harry Potter and the Prisoner of Azkaban, Chapter 12 (The Patronus)
Yet Arthur can't even get the word for electricity right. As further evidence that wizarding knowledge of the Muggle world was accurate, Hermione, a Muggle-born who that same year had been complaining about the fallible nature of Divination, hadn't complained once about the information in her Muggle Studies class being wrong. In fact, she recommends that Ron take it - which she wouldn't have done if it would have just given him misinformation.
“Harry, you’ve got to come and stay with us. I’ll fix it up with Mum and Dad, then I’ll call you. I know how to use a fellytone now –’
‘A telephone, Ron,’ said Hermione. ‘Honestly, you should take Muggle Studies next year …” - Harry Potter and the Prisoner of Azkaban, Chapter 22 (Owl Post Again)
Now it's unlikely that Draco would be taking Muggle Studies, but if other wizards around him knew about helicopters, someone could have mentioned them to him.
Hatred doesn't necessarily prevent someone from having knowledge about a subject and hating something doesn't make someone forget everything they might happen to learn about it. So it's entirely possible that even as a member of a pure-blood family with no interest in Muggles, Draco could have learned what a helicopter is somehow and retained the knowledge.
But it's very unlikely that Draco's boasts about escaping helicopters are true.
If Draco was flying close enough to Muggles to be narrowly escaping them, he'd have been violating the Statute of Secrecy. While the Trace only becomes effective after wizards get their wands and magic before then is generally written off as accidental, if he was flying a broom near Muggles there would likely be consequences. In addition, while Lucius would certainly have the money and the influence to prevent Draco getting into too much trouble, he'd likely be furious with Draco if he flew in front of Muggles since he was very interested in keeping an appearance of propriety.