The Red Devils are reportedly looking into plans to increase the capacity of Old Trafford from 76,000 to 88,000, the Metro reports.
The stadium underwent an increase from 67,500 to its current capacity in 2006, but it is believed further plans for expansion were blocked by the existence of a train track behind the south stand.
Old Trafford is currently the biggest club ground in England, but the gap has been reduced in recent years by Arsenal, Liverpool, West Ham, and will be by Tottenham Hotspur when they complete their 61,000 stadium in 2018.
United announced earlier in the year that they plan to reduce the capacity of their stadium to 73,000 to build sections for disabled supporters, but it is believed this might become part of a bigger building project in bid to raise the capacity by 15,000 more seats as well.
The potential increase could make Old Trafford the second biggest club ground in Europe, only behind Camp Nou.
Here are the top 10 European club grounds currently:
| Club | Stadium | Capacity |
| Barcelona | Camp Nou | 99,354 |
| Borussia Dortmund | Westfalenstadion | 81,356 |
| AC Milan | Stadio Guiseppe Meazza | 80,018 |
| Manchester United | Old Trafford | 76,000 |
| Bayern Munich | Allianz Arena | 75,000 |
| Hertha Berlin | Olympiastadion | 74,649 |
| Lazio and Roma | Stadio Olimpico | 72,698 |
| Zenit St Peterburg | Krestovsky Stadium | 68,134 |
| Atletico Madrid | Wanda Metropolitano | 68,000 |
