Lonnick admitted that if United qualify for the Champions League, their player goals in the summer transfer window will be easier to achieve.
United have been outside the top four in the Premier League since 16 October, but if they beat West Ham at Old Trafford on Saturday, they could rise to fourth in at least 24 hours.
Ronnick's side will face Atletico Madrid in the 16th round of the Champions League next month, but the league and knockout routes to reach the Champions League are fiercely competitive.
United are currently finalizing their top summer target list with a view to executing trades starting next month, but their european status for next season is unclear.
"Yes, of course, if we knew we were going to play in the Champions League next season, it would be helpful," Lonnick said. "Not only for potential new players, but also for the players we already have here.
"Everybody wants to play in the Champions League, but as I said, there are only two ways to play in the Champions League next season, or you get the top four in the Premier League – it's not easy this season because there's a lot of competition – the other way is to win the Champions League yourself.
"We all know that neither of these things is easy, but it is more realistic and more likely than to just say from now on that we plan to try to win the Champions League, plan and move on to the top four in the Premier League. That's exactly what I told the players before Brentford kicked off. "
After the match against West Ham, the United players will have a week off and will resume training on 29 January before heading to Middlesbrough in the fourth round of the FA Cup on 4 February.
The upcoming gap is not a winter break, as federations outside Europe hold World Cup qualifiers and the Africa Cup of Nations is over and United will not embark on a warm training journey like in 2020, when they spent almost a week in Malaga.
Tres and Fred are playing in Brazil and Cavani has been called up by Uruguay. Langenick also hinted that some players would not be able to travel, which seemed to refer to those who had not been vaccinated against COVID-19.
"The players will have a few days off," Langenick explained. "Then we will resume training on Saturday and have a normal full training week before the game against Middlesbrough.
"I think it's more important than two weeks of training, going to a training camp, whether it's going to a country or going back to England, you're going to face all the limitations. This would have made no sense.
"There may even be a few players who can't get on the plane, so it doesn't make sense to travel with two-thirds of the players. We have four players out playing in the offseason, so it doesn't make sense to travel with only half or two-thirds of the players. "