Senior Full-Stack Engineer (App Team) in London

Who we are 🌍 We’re IAG Loyalty - one organisation with two ambitious, growing divisions across Loyalty and Holidays. Each has its own goals, strategy and team, but together we’re united by a shared vision to create a more rewarding world of travel and experiences. Our Loyalty division is home to Avios, the global loyalty currency, enabling millions of members to collect and spend rewards across travel, retail and financial services. Our Holidays division including British Airways Holidays and Iberia Vacaciones, brings together trusted brands, connecting customers to thousands of destinations worldwide through seamless, end-to-end travel experiences. We’re on an exciting journey of growth and transformation – we’re going places.

The opportunity ✨ Join IAG Loyalty and help shape the continued development of the Avios App, a global loyalty platform used by millions of travellers worldwide. As a Senior Full Stack Engineer, you’ll lead the delivery of complex, high-impact features across both mobile and backend systems. You’ll bring deep expertise in either React Native or .NET/C#, alongside strong hands-on experience in the other, and will be expected to operate confidently across the full stack. We are deliberately hiring engineers who are strong in one domain but credible and effective in the other—whether that’s a mobile-first engineer who understands backend systems deeply, or a backend-first engineer who can confidently contribute to mobile development. Working within a dedicated product team, you’ll play a key role in shaping solutions, guiding implementation, and raising engineering standards across a platform used by millions of customers.

What you’ll be doing 🚀 You’ll take ownership of delivering features end-to-end across the Avios App, working across both React Native and .NET/C# to build scalable, reliable solutions. While you’ll naturally lead in your core area of expertise, you’ll also contribute meaningfully across the wider stack—collaborating with teammates to ensure features are designed and delivered holistically rather than in silos. Day to day, you’ll work closely with engineers, QA, Product Managers and Designers to break down complex problems and turn them into well-designed, production-ready solutions. You’ll be expected to bring strong technical judgement, helping to shape implementation approaches, challenge decisions where needed, and ensure a high bar for quality, performance and maintainability. You’ll also play an important role in supporting the wider team—contributing to code reviews, mentoring other engineers, and helping to continuously improve engineering practices across the platform. This includes identifying opportunities to improve scalability, reliability and developer experience, as well as contributing to a culture of ownership and continuous improvement.

What we need from you ⚡

• Strong experience delivering customer-facing applications at scale
• Deep expertise in either React Native or .NET/C#
• Strong hands-on experience in the other — able to confidently read, debug and contribute to production code
• Experience delivering features end-to-end across mobile and backend systems
• Clear understanding of how mobile and backend systems interact in a production environment
• Strong understanding of APIs, distributed systems and cloud environments (AWS preferred)
• Experience with CI/CD, automated testing and modern engineering practices
• Ability to contribute to technical discussions and influence implementation decisions
• Experience mentoring engineers and raising engineering standards
• Strong communication and collaboration skills

We might not be right for you if:

• You only want to focus on your to-do list; we’re a small, high-performing team, we help each other to succeed.
• You value perfection over fast iteration and progress; IAG Loyalty moves fast, we learn and iterate as we go; our environment isn’t right for everyone.
• You’re looking to create but not build; this is an end-to-end role, you need to be comfortable owning your space, from ideation through to delivery and review.

If you think you have what it takes but don't meet every single point above, please do still apply. We'd love to chat and see if you could be a great fit.

The Blend 📍 This role will work as part of our Loyalty Division and is based out of our London office. We call our approach to hybrid working The Blend — it’s about giving you the flexibility to choose where you do your best work, while staying connected with your team and the wider business. This means you will be required to spend at least two days per week in the office, with the rest of the time working from home. You may also be required to work from one of our other office or partner locations, based on your role and 'to do' list.

What Makes Us Special You do! Our people bring the energy, the warmth, and the ideas that make the business extraordinary. As we grow, you’ll have the chance to grow too — with real opportunities to develop your skills and your career.

Diversity and Inclusion Our vision is to create a more rewarding world of travel and experiences. Delivering that requires diverse thinking and inclusive leadership. We are committed to building a workplace where people feel they belong and are valued for their perspective. Inclusion drives better decisions, stronger performance and more innovative outcomes. We actively encourage applications from people with different experiences and backgrounds, and are committed to ensuring our recruitment process is fair, inclusive and accessible.