## 2 Literature Review  
The utilitarian, user-friendly, and accessible nature of mobile devices has made them indispensable tools for fulfilling human needs in recent years [22]. One of the key drivers of the success of mobile devices is the extensive use of mobile applications. Unlike traditional software systems, mobile applications require new approaches to understand and maintain their functionality [3].  
Initially, mobile applications were limited to basic productivity and information retrieval tasks, such as email, calendars, and weather. However, the increasing demand from users and the proliferation of developer tools have expanded applications into diverse domains [1]. Over time, mobile apps have become integral to everyday life, encompassing categories like social networking, gaming, finance, education, and travel [23].  
Among these, mobile travel applications have become critical tools for tourists, enabling them to plan trips, compare prices for travel and accommodation, and complete bookings [10; 24; 25].  
Applications such as Booking.com and Expedia are prominent examples that offer significant user bases and a unique user experience. Booking.com, based in the Netherlands, supports over 500 million users in 43 languages and provides access to more than 28 million accommodation listings [26]. Meanwhile, Expedia, a U.S.-based app, serves over 50 million users in 70 countries and offers a wide range of travel-related services [27].  
The preference for mobile applications among users is driven by key factors such as efficiency, satisfaction, learnability, memorability, and error handling [28]. For instance, efficiency refers to the ability of users to achieve their goals with minimal resources, while satisfaction involves relieving discomfort and fostering positive attitudes. Learnability ensures that the application is easy to understand, even for first-time users, and memorability allows users to re-engage with the system without the need for relearning. These attributes collectively shape the user experience and serve as benchmarks for app providers aiming to refine their strategies [29].  
Beyond functionality, consumer relationships with mobile applications are strongly influenced by perceptions of trust, reliability, and reputation. A brand's online reputation, often defined by user sentiment, plays a critical role in evaluating its credibility [30]. This reputation is increasingly shaped by consumer reviews and comments on online platforms, which offer insights into the perceived quality of an application [31].  
Recent advancements in sentiment analysis and topic modelling have proven invaluable in uncovering user perceptions and improving application quality [10]. These methods allow developers to identify patterns in user reviews, predict customer sentiments, and effectively address specific needs [32]. [PERSON] et al. [14], for instance, proposed a multifaceted sentiment analysis approach to measure dimensions in consumer comments, though their work did not fully explore the impact of textual feedback on mobile applications.  
While previous studies have examined user sentiments and app functionality, there is limited research focusing on how sentiment analysis and topic modelling can provide actionable insights for the mobile travel industry. This study fills this gap by analysing user reviews from two leading travel apps, Booking.com and Expedia, using advanced data analysis techniques. By integrating these methodologies, it not only contributes to the existing literature but also offers practical recommendations for app providers seeking to enhance user satisfaction and manage brand reputation. Table 1 shows a comparison of previous studies.  
This study provides important insights into mobile travel apps through the innovative use of sentiment analysis and topic modelling. This gap in the literature is filled by an in-depth analysis of user feedback from major apps, such as Booking.com and Expedia.